RACHEL MARTIN, HOST:
The other day, my 8-year-old Wyatt picked up a book about the human body. He started reading out loud, and then the questions came on fast.
WYATT: Your heart beats 100,000 times a day, pumping 2,000 gallons of blood through your body. That's amazing. How many blood does your heart even have?
MARTIN: And that's what the book was designed to do. It's called "The How And The Wow Of The Human Body." It's written by two people who know a lot about channeling kids' curiosity and wonder - Guy Raz and Mindy Thomas. They are also the hosts of the hugely popular podcast Wow In The World. And the world encompasses a lot, right? So I asked them how they settled on doing a book about what happens in our bodies.
MINDY THOMAS, BYLINE: This is something that every kid could relate to. And why not start there? Let's understand ourselves before we even get out in the world.
MARTIN: You were into this idea, Guy?
GUY RAZ, BYLINE: Yeah. I mean, when I was a kid, I used to love books like "The Way Things Work." I used to love playing Operation. And when we were talking about a way to explain the magic in the world, we immediately went to the human body. I mean, it is the most complex machine in the known universe - full of amazing (laughter) parts and movements and so visual.
MARTIN: Sounds (laughter).
THOMAS: Yeah, and so that's the other thing - it's also just really gross. And so we thought - you know, it leaks.
(LAUGHTER)
THOMAS: Like, we have a computer in our heads, and we also leak. So why not write a book about the combination of this incredibly complex piece of machinery, more complex than anything we'll ever experience, that also makes funny sounds and, you know, produces gross things?
RAZ: (Laughter).
THOMAS: And that combination is kind of what we do best. That is - to us, that's wow and wonder.
RAZ: And we needed something to make us laugh all the time, which is what Wow In The World does.
THOMAS: (Laughter) Yeah.
RAZ: So that's what this book did, yeah.
MARTIN: I mean, I do love that you lean into the gross stuff, and it is awesome. And I learned things. For example - I am quoting here, Page 19 - "Your nose makes about one quart of snot every single day, and you swallow most of it."
(LAUGHTER)
MARTIN: Things I didn't know.
RAZ: Yeah, yeah.
MARTIN: And things my kids are so into. And there's also - guys, there's just - there's a lot about poop in here. Can we just say?
THOMAS: Yeah.
MARTIN: A lot. You know, obviously, we know - I mean, it's a biomarker, right? And it's also a really interesting thing that we produce, right?
THOMAS: Yeah, I love that there is a scale out there that shows you, you know, the size, the color, the weight, the consistency of your poop, what that can tell you about your body. That was life-changing for me.
MARTIN: (Laughter).
THOMAS: I suddenly went from never paying attention to that, to all of the sudden being like, oh, I need some more fiber. I need some more water in my diet.
RAZ: Yep.
THOMAS: And I think kids will look at this and think the same thing. It's super accessible.
MARTIN: Well, I'm just also excited to diversify the conversations in my house that occur around poop because the word is uttered so often, but it's a fairly one-dimensional conversation.
RAZ: (Laughter).
MARTIN: So I'm excited to bring, you know, a little more science and heft to those references.
RAZ: Yes, indeed.
THOMAS: For sure.
MARTIN: So also, I just want to point out - there's just fun and information on every page. I randomly this morning just opened it and wanted to see where I fell, and I fell on Page 90 about armpits, which is just the best. And it kind of represents what you're doing in this book because there's science. There are tips. There's all kinds of information here. And I was wondering, Mindy, would you mind reading a little bit of this section? It's about what armpits can tell you about your body, right?
THOMAS: I'd love to.
(Reading) Are you sick? Ask your armpits. While your armpits can't speak - if they do, you should consult your doctor - they can tell you how well you're doing. Each armpit contains a bunch of little lymph nodes. Lymph nodes are like teeny-tiny bean bags sitting under the surface of your skin, and their job is to filter out and fight off bad germs that can make you sick. Most of the time, you can't see or feel them. But if you do feel them, it's most likely because they're swollen, and swollen lymph nodes can be your armpits' way of telling you you've got an infection.
MARTIN: I love that. And also, Guy, why can't you tickle yourself in your armpits?
RAZ: Well, it's not entirely clear why. But a group of scientists from the University of Cambridge in the U.K. think that it may have something to do with your cerebellum, which is the part of your brain that kind of anticipates, prepares you to know what things are going to feel like. And so when you tickle yourself, your cerebellum knows what to expect, so it's not surprised. So you can't tickle yourself.
MARTIN: You have to be surprised to get tickled.
RAZ: Yeah.
MARTIN: So my son and my editor's daughter are both in third grade, and they were both really into this book. And it's probably, like, prime demo, I'm thinking...
THOMAS: Oh, yeah.
MARTIN: ...For this book (laughter), third grade. And they each have some questions for you guys. Let's listen.
NURA NIA: Hello, I'm Nura Nia. I'm 8 years old, and my question for you is, why do we have to brush our teeth?
RAZ: Well, here's the thing about teeth-brushing. It's kind of a pain, right? We have to do it at least twice a day, at least for two minutes at a time. And, you know, our mouth produces a lot of bacteria, and if we don't clean our teeth and scrub it away, it starts to get into our gums and starts to create gum disease and cavities, and then our teeth eventually rot and fall out. And it's not just gross, but it's also really painful.
THOMAS: But I would say, you don't have to brush all your teeth, just the ones that you want to keep.
MARTIN: There you go.
RAZ: (Laughter).
THOMAS: That's for adults.
MARTIN: There you go.
THOMAS: Kids, you should brush them all, even the ones that are temporary, disposable teeth.
(LAUGHTER)
THOMAS: You got to brush them all.
MARTIN: All right. And here's Wyatt.
WYATT: Hello, Mindy and Guy. I'm Wyatt. And my question is, why do we need our wisdom teeth?
THOMAS: Well, Wyatt, I am here to tell you that, actually, we don't need our wisdom teeth. They are left over from our early ancestors who used to munch on leaves and roots and raw meat. But, you know, times have changed. We eat soft things now - lots of mac and cheese and ice cream and marshmallows. And we no longer need these wisdom teeth.
RAZ: (Laughter).
THOMAS: So there might come a time in your life where you just have a dentist say, we got to get them out of there.
MARTIN: Milkshakes all day. So much information. Mindy Thomas and Guy Raz, co-hosts of Wow In The World and authors of the new book "The How And The Wow Of The Human Body." You guys, thank you so much. This has been so fun.
THOMAS: Thank you, Rachel.
RAZ: Thank you, Rachel.
(SOUNDBITE OF SONG, "BRUSH YOUR TEETH")
THE WIGGLES: (Singing) Two minutes to brush your teeth.
MARTIN: I assumed you guys learned things, too?
THOMAS: Oh, yeah.
RAZ: So much. I did not know that humans are the only animals with chins.
MARTIN: Chimpanzees don't have chins?
RAZ: No.
THOMAS: I thought it was interesting to find out that kids actually have juicier earwax than grown-ups.
MARTIN: Gross.
THOMAS: Yeah.
RAZ: Yeah. And kids' fingernails grow twice as fast as grown-ups, which makes total sense because I'm always clipping my kids' fingernails, like every other day.
(SOUNDBITE OF SONG, "BRUSH YOUR TEETH")
THE WIGGLES: (Singing) Morning and night for your healthy gums and teeth. Transcript provided by NPR, Copyright NPR.