vesicle
A vesicle is a small, spherical compartment that is separated from the cytosol by at least one lipid bilayer. Many vesicles are made in the Golgi apparatus and the endoplasmic reticulum, or are made from parts of the cell membrane by endocytosis. Vesicles can also fuse with the cell membrane and release their contents to the outside. This process is called exocytosis. In addition to the Golgi apparatus and ER, vesicles can also fuse with other organelles within the cell.