Exocytosis is a cellular process in which materials are transported out of a cell through the fusion of vesicles with the plasma membrane. This mechanism is crucial for the secretion of substances, such as hormones, neurotransmitters, and enzymes. During exocytosis, the vesicle membrane merges with the cell membrane, releasing its contents into the extracellular space. It plays a vital role in various physiological functions, including communication between cells and the maintenance of cellular homeostasis.