Endocytosis is a process whereby cells engulf and take in material that lies outside their cell membranes. Endocytosis involves the formation of a vesicle called an endosome from part of the cell membrane. The food is eventually engulfed into the vesicle, which then moves further into the cell where it meets a lysosome. Within the lysosome are digestive enzymes that break down the food.


Endocytosis comes in three forms: phagocytosis ("cell eating"), pinocytosis ("cell drinking"), and receptor-mediated endocytosis. The opposite of endocytosis is exocytosis.