Light micrograph of a section through skin showing four hairs (black). Hairs are made up of dead tissue. The are are pushed up by growth from the bulb (not seen) at the base of the follicle, which lies in the dermis layer of the skin. The outside of the hair, the cuticle, is covered in overlapping scales that protect the hair's central cortex, which is made up of the fibrous protein keratin.