Pinocytosis. Illustration of the process of pinocytosis, by which cells engulf liquids (here, solute molecules, orange). The solute molecules are enclosed by an area of cell membrane as it enfolds or 'invaginates' to surround them (centre left). This invagination pinches off (upper right) to form an enclosed vesicle (lower right) within the cell cytoplasm (blue). Pinocytosis is a form of endocytosis. For three forms of endocytosis, see images C023/8788, C023/8790 and C023/8795. For exocytosis (the reverse process), see image C023/8797. For this artwork with labels, see image C023/8789.