Hair

biology · mammals · skin · keratin

Made of protein. Hair is primarily composed of a protein called alpha-keratin, the same tough protein found in your nails and the outer layer of your skin. This protein gives hair its strength and flexibility.

Covers most of your body. Your entire body, except for smooth areas like your palms and lips, is covered in hair follicles that produce hair. Most of this hair is fine and barely visible, but some is thicker and darker.

Mammal signature feature. Hair is one of the main things that makes mammals different from other animals. Every mammal, from whales to bears to humans, has hair at some point in its life.

Grows from follicles. Hair grows from tiny pouches in your skin called follicles, which are located in the layer underneath your outer skin called the dermis. Each follicle is like a little factory that produces a new hair.

Strong biomaterial. Hair is classified as a biomaterial because it's a strong, useful substance produced by living things. Scientists study hair's properties to understand how to make better materials.