Hair follicle. Coloured scanning electron micrograph (SEM) of a longitudinal section through a freeze-fractured hair follicle. The skin surface (not seen) is towards top. The hair shaft (yellow/ brown) ascends through the skin to top centre. The hair shaft grows from a structure called a hair follicle. Several associated structures are seen, including a sebaceous gland (honeycombed, pink, lower frame) that produces the sebum that oils the hair and skin. The compact structures (purple and green, top left) are parts of the arrector pili muscle that allows the hair to stand on end. Hair consists of the fibrous protein keratin. Magnification: x200 at 6x7cm size.