Exocytosis is the process where molecules produced inside a eukaryotic cell are secreted out of the cell through the fusion of membrane-bound vesicles with the plasma membrane. For example, secretory proteins that are destined for exocytosis, first leave the endoplasmic reticulum packaged along with other vesicular components in a transport vesicle. This cargo proceeds through the cisternae of the Golgi apparatus, continuously budding and fusing until the contents reach the trans-Golgi network. Here they bud off into vesicles once again and finally head towards their target, the plasma membrane, where the membranes of the vesicle and cell fuse, releasing the signal into the extracellular space.