Cholesterol is a lipid found in the cell membranes and transported in the blood plasma of all animals. It is an essential component of mammalian cell membranes where it is required to establish proper membrane permeability and fluidity. Cholesterol is the principal sterol synthesized by animals while smaller quantities are synthesized in other eukaryotes such as plants and fungi. In contrast cholesterol is almost completely absent among prokaryotes. Most cholesterol is synthesized by the body but significant quantities can also be absorbed from the diet. While minimum levels of cholesterol is essential for life, excess can contribute to diseases such as atherosclerosis. Cholesterol is classified as a sterol (a contraction of steroid and alcohol). The name cholesterol originates from the Greek chole- (bile) and stereos (solid), and the chemical suffix -ol for an alcohol, as researchers first identified cholesterol in solid form in gallstones by François Poulletier de la Salle in 1769. However, it is only in 1815 that chemist Eugène Chevreul named the compound "cholesterine". (via Wikipedia)