Root of hair. Historical artwork of the root of a human hair (brown). Hair consists of dead cells containing keratin, a fibrous protein. The root of each hair is embedded in a skin follicle (pink). The root is surrounded by a bulb (globular, brown), which contains living tissue and supplies the hair with keratin. Hair is formed when new cells produced in the root (lower centre) push up older cells, which then become keratinised.