False-colour scanning electron micrograph (SEM) of crystals of cholesterol, a sterol, a fat-like material synthesised by all animal cells. It is a major constitutent of the cell membrane, a precursor to the formation of sex hormones & the source of bile salts. A third of body cholesterol is made in the liver. Its excretion, directly or as bile salts, is the sole responsiblitiy of the liver. Body cholesterol is added to by dietary cholesterol from meat & dairy products. High levels are associated with atheroma & coronary heart disease but the relationship is unclear. Magnification: x290 at 35mm size, x580 at 6x7cm size.