Triglycerides are composed of two types of molecules: glycerol (a 3 carbon molecule) and fatty acids which attach to the glycerol at the alcohol unit. The following is a structural representation of a triglyceride at the molecular level:

Fatty acids are chains of hydrocarbons 4-22 (or more) carbons long with a carboxyl group at one end. If each carbon has 2 hydrogen atoms the fatty acid is saturated. If two carbon atoms are double bonded, so that there is less hydrogen in the fatty acid, it is unsaturated (monounsaturated). If more than 2 carbon atoms are unsaturated, the fatty acid is polyunsaturated.