Vesicle
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. Vesicles can fuse with the plasma membrane, and release their contents outside the cell. Vesicles can also fuse with other organelles within the cell.