About skin: Your body's largest organ

Is your epidermis showing? Don't worry, it should be. Your epidermis is the top part of your skin, and your skin is your body's largest and fastest-growing organ. Skin is your body's coat. It protects you. It helps you stay warm when it's cold, and cool when it's hot. Your skin keeps all your insides in, from your heart and lungs to your blood and muscles. And unless it's cut or damaged, it keeps stuff out, including germs and water. You also feel things through the nerves in your skin.

Doctors who are experts in caring for skin are called dermatologists. Derma is the Greek word for skin. Dermatologists treat just about everything that can happen to skin, including rashes, dry skin, acne, and skin cancer.

Next: How skin grows