Hair is composed of a protein called keratin, produced in hair follicles in the outer layer of the skin. Each follicle contains a hair bulb, where living cells divide and grow to build the hair shaft. The hair shaft has three layers: the cuticle, cortex, and medulla. The cuticle is the outermost layer, protecting the inner layers. The cortex provides strength, color, and texture, while the medulla is the innermost layer, often absent in thinner hair.
