Red blood cells. Coloured scanning electron micrograph of red blood cells (erythrocytes). These cells have a biconcave disc shape and a flexible structure. They contain the red pigment haemoglobin with which they transport and supply oxygen to the body. Some of the red blood cells are crenated (spiked, orange/yellow). This occurs due to osmosis when a blood sample is exposed to a concentrated solution. It may be symptomatic of uraemia (accumulation of nitrogenous waste in the blood) but more usually is the result of prolonged storage of a blood specimen. Magnification x600 at 6x7cm size.