High Quality Content by WIKIPEDIA articles! A vesicle is a bubble of liquid within a cell. More technically, a vesicle is a small, intracellular, membrane-enclosed sac that stores or transports substances within a cell. Vesicles form naturally because of the properties of lipid membranes (see micelle). Most vesicles have specialized functions depending on what materials they contain. Because vesicles tend to look alike, it is very difficult to tell the difference between different types of vesicles without sampling their contents. The vesicle is separated from the cytosol by at least one phospholipid bilayer. If there is only one phospholipid bilayer, they are called unilamellar vesicles; otherwise they are called multilamellar. (Lamella means membrane).