Hair follicles. Coloured light micrograph of a section through hairs of the human skin. Many hair shafts (circular structures) are seen embedded in the dermis (white) of the skin. Epidermis (yellow) surrounds each hair as an ingrowth of the skin surface. Hair consists of an outer cuticle layer of cells and an inner cortex (orange) that contains the pigment which gives hair its colour. The shaft also has a central core or medulla (green) that may sometimes be hollow (bottom, white centre). Hair is made of the fibrous protein keratin. Most hair cells are dead except for a growing bulb region at the base of the hair shaft. Magnification: x20 when printed 10cm wide.