A cell can take up solid and dissolved particles for food in various ways, and endocytosis is one of them. As a result of endocytosis, a living cell forms internal membrane tensions, forming a vesicle with a food particle. When the membrane tension reaches a critical value, the vesicle detaches and forms a vacuole inside the cell.
Subsequently, such vacuoles are cleaved by the internal structures of the cell. Endocytosis is an example of active transport, which means that the free energy of the organism is expended for its realization. For example, by means of endocytosis, an amoeba can form such vesicles and thus seek sustenance.