Phospholipids are phosphoric acid esters of fatty acid, which are major components of all cell membranes. It is well known that the thin polar membrane is made of two phospholipid layers (lipid bilayers) due to the amphiphilic property. As an example of lipid bilayer, liposomes have capsule structure which can contain small amounts of other molecules. Liposomes consisting of phospholipids can be applied to controlled release dosage, drug delivery systems, and cosmetics.