Lipids are heterogeneous group of naturally occurring compounds insoluble in water and soluble in nonpolar organic solvents. They are the major form of energy, provide essential fatty acids, maintain membrane structure and integrity, act as lung surfactant and essential for the absorption of fat soluble vitamins. Lipids are classified into simple, compound and derived lipids. Compound lipids like lipoproteins are of different types like chylomicron, VLDL, LDL, and HDL. The protein part of the lipoprotein is called apoprotein. HDL is good cholesterol and LDL is a bad one because it transports cholesterol from liver to extrahepatic tissues for deposition. Fatty acids are of saturated and unsaturated. The essential fatty acids are those which have to be supplied through diet and they are linoleic acid, linolenic acid and arachidonic acid. Triglyceride is simple lipid which is made of glycerol, one unsaturated and two saturated fatty acids. Lipids are amphipathic in nature. Cholesterol is formed from acetyl CoA which required for steroid hormone synthesis.