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Nuts and Bolts

Dec 03, 2023Dec 03, 2023







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Roma Agrawal [00:02:14] I just kind of wipe the sweat from my forehead going, "Yes, thank goodness that's still there. It's still standing."

Roman Mars [00:02:21] This is Roma Agrawal, one of the structural engineers behind The Shard. Her job is to make sure buildings, bridges, and all sorts of other things withstand the test of time. As a structural engineer, Roma looks at the built world with a special kind of X-ray vision.

Roma Agrawal [00:02:36] So I might consider what the skeleton of the main structure might be–what material is it made from? Where do the main bones of it sit? And so on. And I also might think, "What's underground?" You know, what's actually holding this thing up? How deep does this thing go? So, I’m trying to look beyond the visible.

Roman Mars [00:02:54] When Roma walks past a skyscraper or over a footbridge, she doesn't only see the main structure. She sees all the invisible engineering that makes that design possible–the small, sometimes hidden inventions that hold up our world.

Roma Agrawal [00:03:09] And I have a nut and bolt on my desk right now, and I often just hold it in my palm and think, "If it wasn't for this incredible piece of engineering that sits inside my palm, skyscrapers wouldn't exist." And I think that's kind of humbling. And it just reminds you that great engineering–great design–can be really simple and small.

Roman Mars [00:03:30] Roma recently wrote a book that's actually called Nuts and Bolts: Seven Small Inventions That Changed the World in a Big Way. In it, she takes ordinary objects like the nail, spring, and pump and shows us how these inventions were actually extraordinary feats of engineering in their own right. The concept of Roma's book is a twist on an old idea.

Roma Agrawal [00:03:51] So the Renaissance scientists, engineers–maybe even "artists" you could call them–came up with a list of six simple machines, which were the lever, the wheel and axle, the pulley, the inclined plane, the wedge, and the screw. They saw these as being, you know, types of machinery that made it easier to move stuff or expend energy or use energy in an efficient way. So that was quite a specific view of what machines do. But obviously, you know, the Renaissance was a while ago now, the world has moved on, and things are a little bit different. And I started to think about, you know, even within the very complex technology that we now have–very different from the Renaissance era–what are the little fundamental pieces that I think make up the modern world? And I came up with seven objects. And I always have spirited debates with people, whether they think those are the right seven or should there be more or fewer. But this is my list of seven.

Roman Mars [00:04:56] Today, Roma Agrawal tells us about her seven basic building blocks of engineering and how we might understand ourselves better by taking a closer look at the stuff all around us. Okay, so your book starts–and you start–with the nail. Why the nail?

Roma Agrawal [00:05:15] So if you’re anything like me and you open your desk drawer, there will just be, you know, a few nails kind of rolling around in the bottom of your drawer. They’re cheap, you get them everywhere, we’ve probably all had to go hammering them into a wall to put a picture. And we kind of understand how they work. We kind of get that there's friction involved or that, you know, something is holding two blocks of wood or whatever it is together. But the truth is that, you know, the story of the nail is actually a story of materials. It's a story of humans. It's a story of geopolitics. You know, there's so many different ways you can tell the story of the nail.

Roman Mars [00:05:49] Yeah. And one of the ways you chose to tell the story of the nail is by making one yourself–the old-fashioned way.

Roma Agrawal [00:05:54] Yeah. So, another little thing that I have on my desk is this homemade nail of mine. And it was so interesting to me because I think as an engineer–as somebody who studied science, physics–I thought I understood steel and how it works based on the science of it and how the atoms work and the crystals work and so on. But actually, when you go in to forge a nail, which is how the Egyptians did it, how the ancient Romans did it for thousands of years, it's a completely different experience. It's a very sensory experience.

Roman Mars [00:06:24] Tell me more about that.

Roma Agrawal [00:06:26] So I was in a forge. It has a particular smell. You can kind of smell the burning coke. You put the rod into the flame. It comes out sort of red. And then I was told that red hot is not hot enough and it needed to go kind of orangey yellow–almost glowing. And then you have to quickly take it out, whack it at the right angles, in the right sequence. As it cools down, it starts to sound different–the pitch of the clanging changes. And this is all very, very quick. And it took me, like, four or five cycles to make a nail of heating and hitting and then heating and then hitting. But obviously, the Romans would have done it in one go.

Roman Mars [00:07:17] It's kind of remarkable to think about that for almost everything the Romans built there was a blacksmith somewhere that needed to make the nails. And not just, you know, one nail–thousands and thousands of them all meticulously made by hand.

Roma Agrawal [00:07:30] Yeah. So, the Romans did this funny thing in what is now Scotland, where they were creating a settlement and they suddenly were called away back to Europe and they had to abandon the settlement. And they left a hoard of nails–875,428, to be precise–in a ditch, which they covered up because God forbid that the "local savages" get hold of this incredible material, the iron, but also this incredible piece of technology, this engineering. So, they preferred that it be buried for thousands of years rather than allowing somebody else to use them.

Roman Mars [00:08:10] I mean, I never really considered the idea that the nail could be so valuable because you just see them lying around construction sites and your junk drawer. But they were once a huge part of global trade.

Roma Agrawal [00:08:23] Yeah. So, the materials and the skill to make the nails were both scarce things. And there's a story about how when the British were colonizing the world, they banned the export of nails to their colonies, including the USA. So, if somebody was leaving one house and going to go away and move to a new place or build another house, they actually burned their houses down. And then from the kind of smoking ashes of their homes, they extracted all the nails, bagged them up, kind of swung it over their shoulder, and then went on to build their next house.

Roman Mars [00:09:02] Wow.

Roma Agrawal [00:09:02] So in 1619, a law was actually passed in the state of Virginia to ban people from burning their own houses down and assuring them that, you know, if you were, in fact, going to leave a house and leave the nails intact, that you would be given some kind of compensation for that.

Roman Mars [00:09:22] That is so interesting. And of course, screws, nuts, rivets–they’re around during this time period, too, but just not in the quantities like the nail because before the Industrial Revolution, making those fasteners was really hard. Like, you had to cut each individual thread on a screw manually, too.

Roma Agrawal [00:09:40] Yes. So, nuts and bolts were way more challenging to create because you’d hand cut the outside thread on the bolt and then you had to hand cut the corresponding thread on the inside of the nut and then hope that they fit together. And what I find really fascinating about this is that, you know, we often think that screws, nuts and bolts, rivets are much stronger, better versions of the nail. But the nail is not redundant. The nail is still around. And I think that's, for me, what makes it such a great piece of design–that it's endured.

Roman Mars [00:10:26] Okay, so let's move on to the wheel. Now, the wheel is sort of the quintessential example of the perfect invention. But you have a bone to pick with the way that we think about the wheel.

Roma Agrawal [00:10:37] I do. I mean, there's a phrase that really grinds my gears. I’m sorry, Roman, but I have to go with these nerdy engineering puns.

Roman Mars [00:10:47] Yeah, I know. I got it. The book is full of them. Every time I was like, "Ah, yes. It's so good."

Roma Agrawal [00:10:52] And basically, it's the phrase, "Don't reinvent the wheel." So, this is a phrase that we use in business, in work, in school, all over the place. "No, no, no. We’ve done this thing before. We shouldn't reinvent the wheel." And the reason that this really frustrates me and annoys me is because basically, since humans invented the wheel, we have been reinventing it. I mean, put it this way, if we had not reinvented the wheel, we would not have a single mode of transport that had a wheel on it because wheels were, in fact, not invented for transport.

Roman Mars [00:11:28] Yes. So, this has been a thing that I’ve been quizzing people on since I read your book. And no one gets it. No one gets it. So, for what purpose was the first wheel invented?

Roma Agrawal [00:11:38] So we’re going back in time about 6,000 years now. We’re going to Mesopotamia. And people wanted to create vessels to store their food quickly–robustly–out of clay. And so, your first wheel was, in fact, the potter's wheel. And this was a heavy, large disk, which was made either from clay, from wood, even potentially from stone. And it basically had a little bulge on its underside, which sat in a little pedestal. And then you could spin the wheel within its pedestal. And it would keep spinning thanks to momentum. And they could create pots really quickly.

Roman Mars [00:12:22] And so who was the first person to take this potter's wheel, turn it on its side, and ride on top of it?

Roma Agrawal [00:12:30] It's funny, right? It took potentially somewhere between 1,000 to 2,000 years for someone to do that–just to turn it on its side. And of course, that's because the axle is actually quite a complicated piece of engineering in its own right. And the potter's wheel kind of worked because of gravity, but it wouldn't work on its side. And the first archeological kind of solid evidence we have of a wheel is in a site in the North Caucasus region, which is now in Russia, where archeologists found tens of thousands of ceremonial burial mountains. Some of them were created by the Yamnaya community around the fourth millennium BCE. And one of these graves actually contained a man in a seated position on top of a four-wheeled wagon.

Roman Mars [00:13:21] Buried with what he loved–his own, like, Ford F-150.

Roma Agrawal [00:13:26] Yeah.

Roman Mars [00:13:30] But it's not only this when you talk about the reinventions of the wheel. You know, it wasn't just taking a potter's wheel and turning it on its side. There's sort of the innovation of the axle, which is a big deal. But also, wheels themselves have been innovated over time in numerous ways that you describe. What are some of those ways in which the wheel has evolved itself?

Roma Agrawal [00:13:49] Yes. So, the Yamnaya carts–the example that was found in this grave–was a solid set of wheels. They were made from three planks of wood that were sort of doweled or pegged together. So, you know, here comes the nail or one of its cousins to help us with that. And these would get dragged along by animals. They’re pretty clunky–pretty heavy things. So, when our carpentry skills improved and we were able to use harder metals to create our tools, we then created spoked wheels. And, you know, spoked wheels, of course, are a big iconography in Southeast Asia. The Indian flag has a spoked wheel on it. So, there's a little flag reference for you, Roman. And this was much lighter. So, when you think of the Greeks or the, you know, Romans running around the Colosseum in their little carts and things, they had spoked wheels. They’re much quicker and nimble on their feet. But then when we started looking at flying machines in the 17 and 1800s, designers were thinking, "Well, even spoked wheels are relatively heavy. And if we want to get something up in the air, flying, it needs to be as light as possible." So, then the wire wheel was invented.

Roman Mars [00:15:05] And I should say that the spoked wheels you’re talking about were made out of wood–the kind you’d see on a chariot. But the wire wheel–that's metal. And it's much lighter. It's the kind of wheel that we’re used to seeing on our bikes.

Roma Agrawal [00:15:16] Yeah, it is. But again, in one of those kind of funny things, the bicycle wasn't actually invented until reasonably recently. It's only a few hundred years old.

Roman Mars [00:15:27] Right. You know, I was really intrigued by your explanation of a tire and just what a tire is. Can you say a little bit more about that?

Roma Agrawal [00:15:35] Yeah. So, I mean, I think the word originates from "tie"–like tying together a wheel. And it was when we came up with the spoked wheels made from wood– So you’ve got the hub. You’ve got all these different spokes that are being put into it and then a rim. But they can get shaken apart on the cobbly roads and so on. So, when the Iron Age kind of shifted into Europe, what people did was to heat up rings of iron and then put a ring around the rim of the wheel. But what was very clever is that they did this while the metal was still hot. And so, as it cooled, it shrank a little bit and then compressed the wheel, making it super nice and robust.

Roman Mars [00:16:16] And that thing is a tire.

Roma Agrawal [00:16:17] That thing is a tire.

Roman Mars [00:16:22] The next stop in our tour of seven small inventions that make up the modern world is the spring. So, tell us about the spring.

Roma Agrawal [00:16:29] So springs, I think, are one of the most versatile of the seven inventions that I’ve picked. So, they come in a huge range of shapes–a huge range of sizes. We often think of the coiled metal ones. And in fact, when we’re typing on our laptops, that's what's stopping our keys from permanently sinking down into the depths of our computers.

Roman Mars [00:16:53] I mean, there is a platonic ideal spring in my head, which is like the coiled metal thing, you press down on it, and it bounces back up. But I mean, fundamentally–and I never heard this described before until I read your book–a spring is this device for storing energy and being released when we need it to, which really broke open my mind of all the things that could be a spring, you know?

Roma Agrawal [00:17:22] Yeah. So, trying to describe what a spring is was probably one of the hardest parts of this book for me, actually.

Roman Mars [00:17:32] You did a great job!

Roma Agrawal [00:17:32] Yeah, it kind of broke my brain as well. And I think the first example of a spring… So, with my definition or my attempt at a definition–which is, you know, a material where you can deform it and it stores energy and then you can release that energy and use it in a way that's useful to you–the bow of the bow and arrow is a spring. So, what you’re doing is you’re taking a piece of wood–or in the case of the Mongolian bows, which is what I write about, quite a complex construction of animal bone and tendons, wood, and so on. And you deform it by pulling a string, and you’ve stored some energy in the bow. And then when you release the string, that energy is transferred into the arrow. And so, the arrow can travel much farther–much faster–than would be possible if we just tried to throw it with our arms.

Roman Mars [00:18:25] Yeah. Yeah.

Roma Agrawal [00:18:26] So I think that is the most fundamental or the oldest form of the spring. And you mentioned the coiled metal springs that you squish. You also get coiled metal springs that you pull apart, so on the edges of a trampoline. If you dismantle a clothespin like one might do on a weekend, you’ll find a torsion spring. So that's where you twist it, and it holds energy in twisting. So, it's a very, very versatile piece of design.

Roman Mars [00:18:55] So let's talk about the way that springs are used in buildings. And specifically, you have an example about a concert hall. So how does that all work? And why do you put springs in buildings in this way?

Roma Agrawal [00:19:08] So these springs are on the opposite end of the spectrum to the small springs that we’ve been talking about, like in clothes, pegs, or even inside a mechanical watch. These are springs that, you know, I could wrap around my leg to give you some idea of the size of them. And I was really fascinated by this concert hall in Denmark, which is called the Musikkens Hus or "House of Music." And it's become famous worldwide for having incredible acoustics. So, what is it about a concert hall that is special or unique or that might attract people to pay money and to sit in that space? And when I spoke to the designers, their answer to that was "silence." Achieving silence is actually extraordinarily challenging.

Roman Mars [00:19:55] Yeah. So, I would think inside of a building that the thing that was sort of, like, contributing most to the idea of silence was some kind of, you know, acoustic tiling and baffling and stuff. Where does the spring fit into this?

Roma Agrawal [00:20:10] So the kind of thing you’re describing is very important, and it forms kind of the inside skin of the space that you’re sitting in. The problem comes up when vibrations are coming into the space from the outside. So, the stuff you’ve described–the panels and things–stop echoing, as all podcasters know. It creates that nice flat sound, so you don't have bouncing sound everywhere. But if you’ve got a truck kind of rumbling down the street outside your home, then your panels aren't going to do very much. So, what you need at that point are springs because what the springs do is go, "Ooh, here's some vibrations coming in. I’m going to have a little jump and bounce around. And then I’m going to dissipate that energy into heat. And I’m going to stop that energy from going into the recording studio or the concert hall."

Roman Mars [00:21:06] Okay. So then describe–sort of, like, physically–what does the House of Music in Denmark do with its springs?

Roma Agrawal [00:21:13] The House of Music has got its big main concert hall, and then it's got lots of other teaching rooms and concert halls around the main concert hall. So, the first problem is that you’ve got music from, I don't know, like, a Queen cover band that can infiltrate your Bach concert, which I’m guessing is not a good thing. And so, the idea is, in simple terms, that you’re suspending each one of these spaces, particularly the main concert hall, from springs in all directions–from the ceiling, from the sides of the walls, and on the floor as well.

Roman Mars [00:21:50] So there's basically a room within a room that's attached with springs all around it so that when the world vibrates, it's sort of like that energy is dissipated and so the inner room doesn't vibrate?

Roma Agrawal [00:22:02] Exactly.

Roman Mars [00:22:04] And it's floating in this sort of womb.

Roma Agrawal [00:22:06] That's exactly right. The very technical jargon term for it is "box in box." So, you’re basically creating the inside box. You’ve got springs all around it. And then you have the outside box, which is the ultimate structure. And acoustic engineers then spend a long time interrogating all the different sounds, you know, coming into a building–the different sounds inside a building–and figuring out "How do we arrange the springs in the right way at the right frequencies so that we can create that silence?"

Roman Mars [00:22:46] So this next one is going to be just a quick detour or, you know, interlude of sorts on our journey through the seven inventions. But I wanted to bring it up because the string was definitely around when people decided to list out all the simple machines. Why did you elevate the string to this status?

Roma Agrawal [00:23:03] One of the things that really stuns me about string is that it was invented by the Neanderthals. And we found a six-millimeter-long piece of string which had twisted fibers to make this, you know, piece of engineering. And we use almost exactly the same principle to hold up some of the biggest bridges on our planet today.

Roman Mars [00:23:30] And when you look at a cross-section of, you know, a cable from a suspension bridge, it really is just, like, a cross-section of string. It has all these little threads around little big threads put together into one big rope type of thing that's all made out of metal. It just looks… It is string.

Roma Agrawal [00:23:48] It is. Completely. And that's what I really love about it. And I think the other thing I also love about it is just how beautiful it is. String is beautiful. It creates beautiful things–not only physically beautiful things–but also music. And where would we be without music?

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Roman Mars [00:27:45] And so our next entry in your Seven Inventions for Making the Modern World is one that the engineers during the Renaissance probably never would have considered at all. And that's the magnet. Tell me why you chose magnets.

Roma Agrawal [00:27:57] Yeah, I mean, I chose them because they’re really attractive.

Roman Mars [00:28:04] Roma!

Roma Agrawal [00:28:04] I know, I know. I’m going to stop. So, magnets, as you say, were strictly not an invention perhaps. They were discovered in the form of what we now call "lodestone." So, there is a form of iron called "magnetite." And magnetite is found naturally in the world. And so, the ancient Chinese found some of it and were known for creating some of the very early compasses, using it for navigation. But we really didn't understand what magnetism was and how it worked. And then fast forward a few thousand years, when we figured out electricity coming into the kind of 18th, 19th centuries, we suddenly realized that electricity and magnetism are in fact very intertwined.

Roman Mars [00:28:58] So, you know, when it comes to describing the importance of magnets, what objects or what sort of engineering feats did you use to explain that?

Roma Agrawal [00:29:08] Yeah. So, I mean, I think magnets are really, really key. Magnetism is very key to long range communications. And the engineer that I talk about is called Jagadish Chandra Bose. And he's an Indian scientist, and he used to work kind of in colonial India. So, in a way, it was fortunate that he was able to do the research that he did. And what he figured out is with this interaction between electricity and magnetism, you could use electromagnetic waves. So light is an electromagnetic wave. But he was looking at radio waves–slightly different–that you could transmit energy and transmit signals.

Roman Mars [00:29:50] I mean, of all the inventions in your book, this is the one where, you know, there's not a physical connection to make the thing work. I don't know. I feel like… I don't get high. But I feel like, if you get high, this is what you begin to think about. You know, just, like, how mind blowing it is to think that a force is exerted across a room, what that means, and how revolutionary that is.

Roma Agrawal [00:30:17] Yeah, it is. And to demonstrate this idea, Jagdish Chandra Bose set up a public lecture in the late 1800s and he invited the lieutenant governor–a British man who had lots of power–got him standing in this room, and then he switched on a transmitter, which generated some electromagnetic waves. And then the waves went through three solid walls and a human body. The waves then arrived at a receiver that he’d set up. And when intercepted, a bell rang, a pistol discharged, and a miniature mine exploded. And this was all intentional; no one was hurt. But he basically demonstrated that we can use these waves to send signals far, far away. And when you talk about this kind of idea of how mind blowing it really is, I think about my grandfather who was sending telegrams a few decades ago–it wasn't that long ago–compared to my daughter who swipes a screen on an iPhone or a smartphone and can place an instant video call to my family in India, thanks to magnetism.

Roman Mars [00:31:37] You mentioned in your book that Bose is a little forgotten in history. And, you know, I imagine a lot of this has to do with where he was working and his identity. But there's also something about his character–that he didn't totally want to own this invention really.

Roma Agrawal [00:31:50] No. So, I don't even know whether he would have been allowed to apply for a patent. I guess it would depend on the powers that be deciding what he could and couldn't do. But as a principle, as a scientist, as an engineer, he didn't believe that knowledge should be restricted. He believed that, you know, knowledge was for everyone. And he wanted to leave a legacy. He wanted to kind of almost create offerings from his life. And he didn't believe that there should be a monetary value attached to that. So even though he invented this incredible device specifically, which was called a "coherer," which did a very difficult job of receiving and interpreting electromagnetic signals of the sorts that he was passing through rooms and people… The radio–Marconi's invention–wouldn't have existed without that. He never patented it. He never restricted it. And I think it's just part of the reason that his name has kind of been lost in history.

Roman Mars [00:32:55] The next invention on your list is the lens. So, tell me about the importance of the lens and how people can understand the lens better.

Roma Agrawal [00:33:01] So I think of it in two extreme ways just in my own life. So one is that I wear glasses. And if I didn't wear glasses, I would have quite a bad headache and not be able to see very well. So even on a very everyday basis, the lens is incredibly important to me. And then there's also the other extreme where I wouldn't have been able to have a biological child had it not been for the lens.

Roman Mars [00:33:23] Oh, well, explain that more.

Roma Agrawal [00:33:25] So this entails starting from a kind of gross/embarrassing story.

Roman Mars [00:33:31] Okay.

Roma Agrawal [00:33:34] So I’m going to take you back to a draper who was called Anthony Van Leeuwenhoek. And this is mid 1600s. He was a bit of a loner, a bit obsessive. And he created these very simple, small magnifying glasses to look at the thread count on the stuff that he was selling. But then he also decided to put other stuff in front of this lens. So, he put blood; he saw blood cells. He put pond water and saw bacteria and algae and all this kind of stuff. And he used to write these really long, descriptive, lyrical letters to the learned gentlemen of the Royal Society in London about his discoveries. One of the letters–let's say–was written in slightly more sheepish tones where he assured the learned men of said Royal Society that the sample that he had looked at was not–and I repeat, it was not–obtained by defiling himself, but were the remains after conjugal coitus. And so, he was the first person recorded to see sperm under the microscope.

Roman Mars [00:34:51] Oh, my goodness. But yeah, he was in great pains to say that he didn't, like, extract the sperm from his own body himself. That would be sinful.

Roma Agrawal [00:35:02] No. And in fact, his exact words, which have been translated from Dutch: "If your Lordship should consider that these observations may disgust or scandalize the learned, I honestly beg your Lordship to regard them as private and to publish or destroy them as your Lordship sees fit."

Roman Mars [00:35:21] Wow.

Roma Agrawal [00:35:22] Another character here.

Roman Mars [00:35:24] Yeah. Quite a character.

Roma Agrawal [00:35:26] And so again, this is one of those funny situations where it took nearly 200 years before we worked out that the sperm and the egg were both involved in the act of fertilization. And then you get to the story of John Rock and Miriam Menken, who were the first to fertilize an egg and a sperm in the lab, paving the way for IVF babies, which is what my daughter is.

Roman Mars [00:35:55] It's so nice. You owe it to a guy who definitely didn't jack off.

Roma Agrawal [00:36:00] Definitely not.

Roman Mars [00:36:08] All right. So, we’ve arrived at the seventh and final invention, which is the pump. Tell me about the pump and its importance to the world of engineering.

Roma Agrawal [00:36:16] So for me, pumps are about life. And I say that because they were invented to support our lives. They were invented to get clean water from a source and bring it to where we lived. They were invented to take disease ridden sewage away from us. They were invented to irrigate crops. But one of the pumps that I actually talk about–and I’m really proud of talking about this because I don't know many engineering books that would talk about this kind of pump–is a pump that I got very up close and personal with soon after I had my baby. And that is the breast pump.

Roman Mars [00:36:53] So talk to me about the breast pump.

Roma Agrawal [00:36:55] I mean, it's not a surprise, really, that I felt like a dairy cow when using these pumps because the original breast pumps were a derivation of the pumps that were, in fact, invented for milking cows, which was invented by a couple of men in Australia. And then, you know, you come into the sort of 19th century and even the early 20th century, and there were all of these really strange contraptions that I don't want anywhere near me that kind of had these big bulbs with tubes coming off them that you had to suck on. Or they just look pretty awful. And I don't even know how they would have worked. And it actually kind of shocked me that it was only really in the 1990s that electrical breast pumps that you could have at home came to market.

Roman Mars [00:37:51] I had no idea it was that late.

Roma Agrawal [00:37:53] It was really late. And if I jump back a little bit into the 1950s, that was the first time an engineer said, "Huh. Let me just think about what's a safe amount of pressure on breast tissue. And let me maybe even measure how many times a minute a baby actually sucks so that the breast pump design can somewhat emulate a baby and be marginally safe for women to use." You know, that took a while.

Roman Mars [00:38:22] Yeah, well, maybe that's why it took till the ’90s–it took that first, you know, like, so you wouldn't be sucked into the machine. But all of it seems extremely late. It points to something that is sort of an undercurrent in your book and I think sort of probably an undercurrent in your life–in the work that I know that you do–is, because women had been excluded from engineering for a long time, these types of innovations… There's these huge blind spots.

Roma Agrawal [00:38:52] Yeah. I mean, from what I could tell–and I mean, listeners, please get in touch with me if this is not the case–I couldn't find breast pumps designed by women until just a few years ago. So, you know, you’ve got men, who are very unlikely to ever use them in their lives, designing things for a purpose that they don't understand, really, or they don't physically experience. And so finally, when women started really looking at, you know, "What do we actually want from the pump? We don't just want the milk. That's not the only purpose of the pump." So, then we started thinking about: "What are actually the correct design criteria for a breast pump?" And that's when, you know, we started coming up with things like it should be silent, they could be discreet, they could use a smartphone–use an app–that's attached to it. And finally, you know, we came up with a design that actually fits inside your bra and that you can walk around with rather than being in a dingy room at the back of your office somewhere strapped to a milking machine. So, I mean, it definitely makes the case for why engineers need to come from all different walks of life.

Roman Mars [00:40:09] Well, it's such a good book. It made me very happy to read. It’ll just give you a greater appreciation for rivets. You’ll just walk around and see rivets, and you’ll go. "I like that rivet. That's a pretty good rivet right there."

Roma Agrawal [00:40:23] Are you saying, Roman, that my book was riveting?

Roman Mars [00:40:27] No, I am not saying that! I am saying that. Your book is very riveting. Thank you so much, Roma. I appreciate it.

Roma Agrawal [00:40:32] Thank you for having me.

Roman Mars [00:40:35] RM: 99% Invisible was produced this week by Jayson De Leon. Original music by Swan Real. Sound mix by Haziq bin Ahmad Farid. Delaney Hall is our Senior Editor. Kurt Kohlstedt is our digital director. The rest of the team includes Chris Berube, Emmett FitzGerald, Martín Gonzalez, Christopher Johnson, Vivian Le, Lasha Madan, Jeyca Maldonado Medina, Kelly Prime, Joe Rosenberg, and me, Roman Mars. An extra special thanks and farewell to Sofia Klatzker who has been my dear friend for decades and came here to help me take this show to the next level and took care of all of us during these huge transitions in the life of the show. There is no amount of gratitude I could express that would adequately thank her for all she did for us. She is moving back to her true calling in the public sector, as the Cultural Affairs Manager for the city of Santa Monica. Her commitment to art and culture being the bedrock of a rich civic life is unparalleled, and she's going to rule at that job. We’re so excited for her, but we’re going to miss her dearly. The 99% Invisible logo was created by Stefan Lawrence. We are part of the Stitcher and SiriusXM podcast family, now headquartered six blocks north in the Pandora Building… in beautiful… uptown… Oakland, California. You can find the show and join discussions about the show on Facebook. You can tweet me @romanmars and the show @99piorg. We’re on Instagram, Reddit, and TikTok too. You can find links to other Stitcher shows I love as well as every past episode of 99PI at

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