Grey hair. Light micrograph of a grey human hair. The surface scales of this single hair shaft are visible, with a silvery sheen. Hair colour is determined by the amount of pigment called melanin in the hair shaft. Melanin is produced by melano- cyte cells at the base of each hair follicle; the activity of these pigment cells is controlled by the pituitary gland in the brain. Red melanin is responsible for red and auburn hair; black melanin for all other colours. If the cells receive no pigment, the outer cortex of the hair becomes transparent and the hair appears grey or white. Darkfield illumination. Magnification: x80 at 35mm size.