Exocytosis is a cellular process where substances are transported out of the cell. This occurs when vesicles containing the substances fuse with the cell membrane, allowing the contents to be released into the extracellular space. This process is crucial for various cellular functions, including the secretion of hormones, neurotransmitters, and the removal of waste products. In contrast, endocytosis is the process of taking substances into the cell, which is the opposite of exocytosis. Understanding these processes is essential for grasping how cells interact with their environment.