Regulated secretion occurs when the ceil detects a signal, vesicles containing the secretory product fuse with the plasma membrane of the cell, and the contents are released into the extracellular space. This mechanism is called exocytosis. Many laboratories around the world have studied exocytosis for the past couple of decades, and we know a lot about the many steps that are involved. The cytoskeleton appears to play a role in allowing vesicles to approach the plasma membrane, and many other proteins are in the cascade between reception of the signal and the release of the secretory products.