What is hair made of?

0:00 Welcome to Science is Not Boring by Kidopoly.com. I'm Mira. And I'm Finn. Today we have a massive shout-out to Hannah, who is sixth, in Melbourne, Australia.

0:11 Hannah loves asking lots of questions, and she asked what hair is made of and how it grows.

0:18 She also wanted to know why it doesn't hurt when we cut it. This one is totally for you, Hannah.

0:23 It is also Hannah's sixth birthday coming up on the 3rd of October, so happy early birthday!

0:29 If you haven't already, tap follow wherever you're listening so you never miss an episode.

0:34 Okay, Mira, I'm ready. What is the mind-blowing fact for today?

0:39 Finn, imagine you have two full-grown African elephants standing next to each other.

0:45 Okay, that is like 12 tons of elephant.

0:48 Exactly! Did you know that the combined strength of all the hair on a single human head could hold the weight of both of those elephants without snapping?

0:57 Wait, what? My hair could hold up 12 tons!

1:01 It absolutely could! Today we are diving into the wild science of hair. What it is made of, how it grows, and why we do not feel a thing when we chop it all off.

1:12 Okay, so if my head can hold two elephants, what is hair actually made of? It can't just be normal skin. It isn't!

1:20 Hair is made mostly of a super tough protein called keratin.

1:24 Keratin? Wait, have we talked about that before?

1:27 Probably, because keratin is the exact same protein that makes up rhinoceros horns, horse hooves, and your own fingernails.

1:36 No way! So I basically have thousands of tiny rhino horns growing out of my head.

1:42 That is one way to look at it, but a hair is far more complicated than a horn. Imagine zooming in on a single strand with a powerful microscope. What does it look like close up? The outer layer is called the cuticle. It isn't smooth at all. It looks exactly like overlapping roof tiles or tiny dragon scales.

2:03 Tiny dragon scales? That is so cool.

2:06 Those overlapping scales protect the inside of the hair. But here is the craziest part, and it answers one of Hannah's biggest questions.

2:15 Why it doesn't hurt to cut it?

2:17 Yes, it doesn't hurt to cut your hair because every single strand you can see on your head is made entirely of dead cells. Ew!

2:25 Wait, seriously? I have a giant mop of dead stuff on my head. Yes!

2:30 Do not panic. That is totally natural, and it is exactly why a haircut is painless. There are absolutely zero nerve endings in the visible hair shaft.

2:41 Okay, but if it is all dead, how does it grow? Dead things do not usually grow. That is the perfect question!

2:50 The secret is that the real action happens completely out of sight, hidden deep underneath your skin. Where exactly? Down in tiny, tube-like pockets in your scalp called follicles. You have about 120,000 of these follicles on your head right now.

3:10 120,000 pockets? My scalp is a busy place. It really is.

3:17 Down at the very bottom of each follicle is a living part called the hair bulb. Think of it like a microscopic factory.

3:26 And this factory is alive.

3:28 Very alive. Blood vessels in your skin plug right into the bottom of this bulb. They pump it full of nutrients, and the factory cells multiply like crazy.

3:39 So the living cells are pushing up from the bottom.

3:42 Exactly. The new cells form at the bottom, and as they grow, they shove the older cells upward toward the surface.

3:50 Ah, so by the time they get pushed out of the skin, they die and harden into those tough keratin dragon scales.

3:58 You got it. And because the dead part has no blood and no nerves, the hairdresser's scissors do not trigger any pain signals to your brain.

4:07 Wait, but if I accidentally yank a hair or someone pulls it, that really hurts. Why does that hurt if it is dead?

4:15 Because you are not just pulling the dead hair. You are yanking on the living root, still anchored down inside the follicle.

4:23 Ouch. That tugs on all the nerves and blood vessels at the bottom of the pocket. Precisely. Snip the top, you feel nothing.

4:32 Pull the root, and your nerves scream.

4:34 Okay, so if the outside is scales, what is inside a hair? How is it strong enough to hold elephants?

4:42 Beneath the scaly cuticle is the thickest layer called the cortex. This cortex is made of long, twisted bundles of keratin fibres.

4:51 Like a really tough rope?

4:53 Exactly like a rope. And those twisted fibres are incredibly strong. A single strand of healthy human hair can hold up to 100 grams of weight.

5:04 100 grams? That is about as heavy as a whole apple.

5:08 Yes, just one tiny hair holding an entire apple without snapping. So if you combine the strength of all 120,000 hairs on an average head, that equals about 12 tons of force.

5:24 Note to self, do not try to lift an elephant with my hair.

5:28 Good idea. Oh, and the cortex does not just give hair its strength, it also contains melanin, which is the pigment that gives your hair its natural colour. What about the very centre of the hair? Is it more rope? Not always. Thick hairs actually have a third layer in the very middle called the medulla.

5:47 What is inside the medulla? More rhino horn? Actually, nothing. The medulla is mostly made of empty air spaces and soft, thin cells.

5:58 Wait, so really thick hair has tiny tunnels of air running right through the middle?

6:03 It sure does. It makes the hair lighter. How fast do you think these hollow ropes actually grow? Um, maybe an inch a day? Slower than that. The factory pumps them out at a rate of about 1 to 1.5 centimetres a month.

6:19 So that is roughly six inches of hair growth in a whole year. Does the Underground Hair Factory ever take a break?

6:25 It does. A single hair will grow continuously for two to seven years. Then the factory shuts down, the hair rests, falls out, and a brand new one starts growing. Two to seven years?

6:40 What happens if you just never cut it?

6:42 That is where the fun facts come in. Most people's hair will eventually stop at a certain length. But some people have incredibly long growth cycles.

6:52 How long are we talking?

6:53 In April 2026, Guinness World Records measured the hair of a woman from India named Renu Darial. How long was it? Her hair was eight feet ten inches long.

7:05 She hasn't cut it since 2015. 8 feet 10 inches? That is taller than the tallest person on Earth. It is!

7:14 And historically, another woman from China named Xia Chuping grew her hair to over 18 feet long.

7:21 18 feet? You could use it as a jump rope. Or a ladder. It would definitely take a lot of shampoo. Okay, so hair is super strong, it can grow ridiculously long, and it is basically dead rhino horn. Why did humans evolve to have it on our heads? It is all about protection.

7:41 Your head is right at the top of your body, directly exposed to the sun.

7:46 Oh, so it acts like a built-in sun hat to block ultraviolet rays. Exactly!

7:51 It also acts like a thermal blanket. The air spaces inside the hair help trap heat, keeping your brain warm in the winter.

7:59 Dead cells keeping my living brain warm? That is surprisingly awesome.

8:04 Alright Finn, time for the quiz.

8:06 Are you ready? I'm ready. Bring on the hair trivia.

8:10 First question. What tough protein is hair made of, which also makes up rhino horns? Next one. What is the outer layer of the hair called that looks like overlapping roof tiles? Question three. How much weight can a single healthy strand of hair hold? Here's number four. Why doesn't it hurt when you cut the visible part of your hair?

8:47 Last question. Roughly how many hair follicles are on the average human head? Great job! Let's see how you did. The first answer is hair is made of keratin. For question two, the outer scaly layer is called the cuticle. Number three, the answer is a single strand can hold about 100 grams, or the weight of an apple.

9:16 Question 4. It doesn't hurt to cut it because the hair shaft is made entirely of dead cells. And the final answer is there are about 120,000 hair follicles on an average head.

9:31 Well, I passed the quiz, but my mind is still totally blown. I am never going to look at my hairbrush the same way again.

9:40 Just remember, you are carrying around 120,000 tiny dragon scale ropes.

9:47 And a factory! Do not forget the Underground Blood Factory.

9:51 If you loved learning all these weird and wonderful facts, please leave us a five-star review. Just scroll down and tap the stars to tell us what you think of the rhino horns on your head.

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10:16 Want your name on the show like Hannah? Send us an email at hello at kidopoly.com.

10:22 Thanks for exploring with us. See you next time on Sciences Not Boring. Bye, everyone. Bye.