Cholesterol is also called cholesterol. It is a derivative of cyclopentane polyhydrophenanthrene. As early as the 18th century, people had discovered cholesterol from gallstones. In 1816, chemist Bencher named this lipid-like substance cholesterol. Cholesterol is widely present in animals, especially in the brain and nerve tissues. It is also found in high levels in the kidneys, spleen, skin, liver and bile. Its solubility is similar to that of fat. It is insoluble in water but easily soluble in solvents such as ether and chloroform. Cholesterol is an important substance that is indispensable to animal tissue cells. It not only participates in the formation of cell membranes, but is also the raw material for the synthesis of bile acids, vitamin D and steroid hormones.