Lipid metabolism is the process that most of the fat ingested by the body is emulsified into small particles by bile and then the lipase secreted by the pancreas and small intestine hydrolyzes the fatty acids in the fat into free fatty acids and monoglycerides. A small amount of fatty acids is completely hydrolyzed into glycerol and fatty acids. After hydrolysis these small molecules, such as glycerol, short-chain and medium-chain fatty acids, are absorbed into the blood by the small intestine. After the absorption of monoglycerides and long-chain fatty acids, triglycerides will be re-synthesized in small intestinal cells and along with phospholipids, cholesterol and proteins to form chylomicron which will enter the blood circulation from the lymphatic system. The liver and pancreas are important sites for lipid metabolism and play an important role in the process of lipid digestion, absorption, synthesis, decomposition and transport.