Capillary. Comparison between a scanning election micrograph (SEM left) and transmission electron micrograph (TEM right) of a capillary. Red blood cells (red) almost filling the lumen (inner space) of the capillary. Capillaries are the smallest blood vessels in the body, only a few micrometres across, just large enough for the passage of red blood cells. The capillary lining consists of endothelial cells. Connective tissue (orange) surround the capillary.Magnification: x4000 when printed 10 centimetres high. For a series of comparisons between SEMs and TEMs see images C047/7006 to C047/7034.