Cholesterol. Macrophotograph obtained with polarised light of crystals of cholesterol. It is a lipid (fatty substance) found in vertebrates and in foods from animal sources. It is largely found in the brain, spinal cord and the liver, the major site of cholesterol synthesis. It plays an important role in the synthesis of vitamin D and the formation of hormones and bile salts. The level of cholesterol in the blood is influenced by diet, heredity and metabolic disorders such as diabetes mellitus. A high level of cholesterol increases the risk of developing atherosclerosis and with it the risk of coronary artery disease or stroke. Magnification: x20 at 6x7cm size. Magnification: x35 at 4x5 size.