False-colour transmission electron micrograph (TEM) showing pinocytosis (endocytosis) in a blood capillary. The lumen of the capillary is at top (blue), with one of the endothelial cells of the capillary lining below, the nucleus of which is red. Pinocytosis refers to the enclosure of extracellular material in vesicles by the cell membrane. A row of these vesicles in formation are seen in the upper cell membrane (purple) & in transit towards the outside of the capillary (bottom). They are involved in the transport of serum. Magnification: x23,000 at 35mm size, x70,000 at 6x7cm size.