Quick! What's the biggest organ in your body?

(a) the heart - because it's so hearty
(b) the brain - you can't do anything without it
(c) the MelodyMaster 1000 - impress your friends when you play the cool keyboard - just send 15 easy payments of $19.95!
(d) the skin

Well, if you guessed (d), you'll be delighted to know that you're quite right! The skin is the body's biggest organ - an adult's skin weighs 5 to 8 pounds (about 3 to 4 kilograms). That's like wearing every single one of your sweaters at the same time! If you spread out your skin, it would measure around 20 square feet (1.8 square meters) in size, about the size of a kid's bedsheet - only without the superheroes or cool patterns printed all over it!

Your skin covers and protects everything inside your body. Without skin, people's muscles, bones, and organs would be hanging out all over the place. It wouldn't be too pretty! And skin is the best when it comes to keeping our bodies at the right temperature. It also protects us from getting hurt, lets us feel things, and more.

So let's not waste any time getting to know the skin!

Don't Miss Your Epidermis
The skin is made up of three layers, each with its own important parts. The layer on the outside is called the epidermis (say: eh-pih-dur-miss). The epidermis is the part of your skin you can see. So no matter how modest you are or how much you cover up, your epidermis is always showing!

Look down at your hands for a minute. Even though you can't see anything happening, your epidermis is hard at work. At the bottom of the epidermis, new skin cells are forming. When the cells are ready, they start moving toward the top of your epidermis. This trip takes about 2 weeks to a month. As newer cells continue to move up, older cells near the top die and rise to the surface of your skin. What you see on your hands (and everywhere else on your body) are really dead skin cells.

These old cells are like veteran sports players: tough and strong, just right for covering your body and protecting it. But they only stick around for a little while. Soon, they'll flake off when you wash, go to the mall, put on your clothes, play video games, sit in class, and sleep at night - all the time!  In fact, every minute of the day we lose about 30,000 to 40,000 dead skin cells off the surface of our skin. So just in the time it took you to read this far, you've probably lost close to 40,000 cells! That's almost 10 pounds (4.5 kilograms) of cells every year! But don't think your skin might wear out someday. Your epidermis is always making new skin cells that rise to the top to replace the old ones. In fact, 95% of the cells in the epidermis are working to make new skin.

And what about the other 5% of the cells in the epidermis, you ask? No, they don't sit around watching TV and munching potato chips. They make a substance called melanin (say: meh-luh-nin). Melanin is what gives skin its color. The darker your skin is, the more melanin you have. And when you go out into the sun, these cells make extra melanin to protect you from getting burned by the sun's ultraviolet, or UV, rays. This is why your skin gets tan if you spend a lot of time in the sun. But even though melanin is mighty, it can't shield you all by itself. That's where wearing sunscreen comes in - to protect your skin from painful sunburns and possibly skin cancer when you get older.