What are your Fingernails made of?
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Psst. Hey, smarty pants, listen up. Take a close look at your finger. Any finger, even your thumb. Careful, don't poke yourself in the eye. So, what do you notice at the end of your finger? Dirt? Pizza sauce? A booger? Eww. More specifically, what do you see at the end of your finger? That's right, your fingernail.

Take a good look at it. Chances are you don't give your fingernails too much thought. Sure, some of you might paint them or chew them or tap them on the table.

And yes, some of you stick them in your nose. But chances are, you take your fingernails and toenails for granted. But did you know they're actually very important parts of your body? In fact, they make humans unique. While many furry mammals have claws...

Primates, such as humans, apes, monkeys, and orangutans have nails. And your fingernails are very useful, like when you have an itch. But there are also some really odd things about your fingernails you might not know. For instance, did you know your fingernails are made of dead tissue? Did you know your fingernails have no nerves in them, which is why you don't scream when you clip them?

At the same time, your fingernail makes your finger more sensitive to the things you touch. Huh? Did you know your nails can reveal things happening inside of you? Whoa. If you want to know what else your nails are good for besides scratching, tapping, picking, chewing on, and painting, then get ready for another whiff of science on...

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Okay, smarty pants, be honest. Do you bite your nails? If so, you're definitely not alone. 20 to 30% of all people bite their nails, including nearly half of all kids and teenagers. Any guesses why so many people do it? Is it to relieve stress? Because they're hungry? Or because it feels good?

The truth is, any of those answers could be correct, since the real cause of nail biting remains a mystery to scientists. What we do know is nail biting is a common nervous habit, and while usually harmless, there is some risk involved in it. You see, nails are like mini shields for your body.

- Fingernails and toenails can prevent viruses and bacteria from getting inside you. But those blocked germs can find a way into your body through your mouth if you bite your nails. Also, you might damage your nails. And as I'm sure some of you know, breaking or cracking a nail can be pretty painful.

While the nail itself is just dead tissue, there are tons of sensory nerve endings underneath your nail. The force of the nail against these nerves makes both fingers and toes more sensitive, which is why your fingertips are so good at sensing cold or heat.

and why your toes feel so much pain when you stub them on a table leg. Now, I just said that your nails are dead. But as you and I know, your finger and toenails grow and have to be cut. So, how's it possible for something that's dead to keep growing? The answer lies here.

Whoa, who are you? How'd you get in here? And what's with the sunglasses? I'm your new neighbor. You left your front door wide open. And these sunglasses protect me from poking my eyes. I've come to show you...

The Matrix. The Matrix? As in an alternate reality created by machines from a movie your parents have probably seen? No, I mean the body part called The Matrix. It's the secret behind your nails.

My name is Phalanx. As in the ancient Greek military formation of troops carrying spears? No, I'm named after the bones in your fingers and toes. I'm sensing a pattern. I smell hamburgers. Oh, yeah, I was grilling earlier. Red meats like steaks and burgers are loaded with protein and iron, which help make stronger nails.

May I have one? Sorry, I ate them all. But I got strawberries and blueberries if you'd like. I see. A red fruit and a blue fruit. Which should I choose? Why not have both? Excellent. Fruits like blueberries and strawberries protect your nails from damage. Salmon, eggs, whole grains, tomatoes, peppers, carrots, almonds, beans and milk.

These foods also help another part of your body. Care to take a guess what it is? Is it A, your hair, B, your teeth, or C, your eyeballs? The smartiest. The answer is A, your hair.

Believe it or not, horses' hooves and bird feathers are made of the same stuff. It's that dead tissue you were talking about earlier. Right, the tissue that's dead but still grows. Do you know what makes it grow? Is it the Matrix? Yes, the Matrix. A body part inside your fingers where keratin cells are made. Those cells start out alive, but they die as the Matrix makes newer cells.

The new cells push the old dead ones out through your skin. That's how your fingernails and toenails grow. Now the matrix is well hidden. But those of us who are aware can see it. All of you. Take a close look at your fingers. Don't poke out your eyes. If your nails aren't painted, you should see something at the base of them. Especially your thumbnail. It looks like part of a whitish circle.

See it? I do. That's the edge of the matrix. Whoa. Nails are always growing from the matrix. On average, fingernails grow between 3 and 4 millimeters a month. Toenails grow slower, only 1.5 millimeters a month from their own matrix. Many factors can impact the growth of your nails. For example, right-handed people's nails grow faster on their right hands.

While left-handed people's nails grow faster on their left hands. Probably because it's your more active hand. Tapping your fingers or typing on a phone or computer can stimulate nail growth. And nails grow faster in the daylight during the summer. Thanks to a lot of nail-strengthening vitamin D from the sun.

And men's and women's nails grow at different speeds. Whoa, who are you? How'd you get in here? And what's with the sunglasses? My name's Lunula. You left your door wide open. And these sunglasses look cool. I'm partners with Phalanx. Have you shown him the Matrix? I have. Lunula. That's an unusual name. It means little moon. I'm named after the part of the Matrix you can see. That whitish half circle or moon. But you can't see it under my long nails. Since they're painted.

That's a lovely shade of... black. But wait, you said men's and women's nails grow at different speeds. So who do you think has faster growing nails? Smartypants, do you think you know? The answer may surprise you. Even though women tend to grow their nails longer than men, men's nails actually grow faster. I did not know that. You know, Lunila, your nails look almost as long as claws. Yes, they're good for scratching, but they're not claws.

Primates evolved from having claws about 2 to 3 million years ago. And there's a good reason why. Take a look at this cat's paws. Wait, I don't have a cat. You really should close your front door. Cats, dogs, and other mammals use their claws to help them climb trees and dig into the ground.

But they're not very good at grabbing small things like board game pieces, Lego bricks, or even a smartphone. It would hurt to pick your nose with claws too. I'm just saying. Fingernails make it easier to use tools, pick bugs off of someone, or turn the pages of a book. Even long nails work better for all that than claws. Though extra long nails can cause some problems, especially nails that haven't been cut for 66 years.

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We've been taking a close look at our nails. Don't poke yourself in the eye. Right. Did you know that your nails, which are on the outside of your body, can actually reveal a lot about what's going on inside your body? It's true. Doctors often look at fingernails to determine if a person has certain health conditions. For example, the shape and color of your nails could reveal lung disorders, iron deficiencies, diabetes, thyroid problems, or kidney and liver diseases.

Or if you accidentally banged your finger or nail, it may change shape and color, especially if you get a bruise. At any rate, check with an adult if you notice anything unusual about your fingernails. Would you call having nearly 30-foot-long fingernails unusual? I sure would. But fun fact, Sridhar Chilal of India let the nails on his left hand grow for 66 years, and they reached a length of 29 feet and 10 inches.

That's like five refrigerators stacked on top of each other. He stopped cutting his nails when he was 14 years old, way back in 1952. He says his teacher inspired his decision. The teacher had a long nail and became angry when Shalal's friend broke it.

When Chalal asked his teacher why he became so angry over a nail, the teacher said Chalal wouldn't understand because he didn't have long nails himself. So Chalal decided to let his nails grow and grow and grow and grow. Chalal couldn't use his left hand for much of his life, but he's proud of his accomplishment and he holds the world record for the longest nails on a single hand.

He's since cut his nails, and they are now on display at the Ripley's Believe It or Not Museum in New York. I don't recommend growing your nails that long. It will keep you from chewing on them or picking your nose like the narrator's doing. What? No, I was just scratching an itch. I swear.

A double shout out to Autumn and Emmy in British Columbia, Canada. We hear you love smarting with us because you love to laugh while learning about our world. Well, if that isn't the best description of who's smarted I've heard in a while, I don't know what is. Thanks! This episode, Nails, was written by Dave Beaudry and voiced by Chris Okawa, Charlotte Cohn, and Jerry Colbert.

Technical direction and sound design by Josh Hahn. Who Smarted? is recorded and mixed at the Relic Room Studios. Our associate producer is Max Kamaski. The theme song is by Brian Suarez, with lyrics written and performed by Adam Tex-Davis. Who Smarted? was created and produced by Adam Tex-Davis and Jerry Colbert. This is an Atomic Entertainment production. Who Smarted?