Underarm hair. Coloured scanning electron micrograph (SEM) of a human underarm hair, showing deposits of sebum (pale brown) and unidentified bacteria (blue rods). The hair shaft consists of dead cells containing keratin, a tough, fibrous protein. Its root, which contains living cells, is embedded in a skin follicle. New cells produced in the root push up the older cells, which become keratinised. Sebum is an oily substance that coats the body, slowing the evaporation of water and providing antibacterial protection. It is secreted by the sebaceous glands through small ducts that lead into the hair follicles. Magnification:x794 at 6x6cm size. x1200 at 4x5 inch size.