False-colour scanning electron micrograph (SEM) of a single red blood cell, or erythrocyte, coloured pink. Nestling in the dish formed by the erythrocyte's biconcave shape is an unactivated platelet, or thrombocyte, coloured yellow. Erythrocytes function in the distribution of oxygen & carbon dioxide around the body. Their shape is adapted for maximum surface area for gaseous exchange; blood gases are carried by haemoglobin, which packs the interior of the red cells. A mature erythrocyte has no nucleus. Blood platelets help repair damaged blood vessels & are involved in the clotting process. Magnification: x5700 at 6x4.5cm size.