There are many techniques available that enable us to know what is happening at the surface of a living cell. These techniques have allowed us to characterize many aspects of the process of exocytosis, the fnal cellular event in secretion. Patch clamping has given us quantitative measurements of the capacitance changes as the membrane of the secretory vesicle is added to the surface of the cell during exocytosis, and the change in the opposite direction as membrane is retrieved back into the cell during endocytosis. Tiny probes have measured electrochemical changes just outside the surface of the cell as reactive molecules are released into their surroundings. Differential interference contrast microscopy has given us high resolution pictures of the cell surface during exocytosis; real-time images are suggestive of bubbles breaking the surface of a boiling pot of water. However, exocytosis is known to be proceeded by an ordered series of events that occur below the surface of the cell.