Endocytosis is the ingestion of material by the cells through the plasma membrane. It is a collective term that describes three similar processes: phagocytosis (cell eating), potocytosis (cell drinking) and receptor-mediated endocytosis. These processes are pathways to specifically internalize solid particles, small molecules ion, and macromolecules, respectively. All of them require energy, so they may be regarded as different forms of active transport.