Blood clot on gauze. Coloured scanning electron micrograph (SEM) of blood clotting on gauze used to dress a wound. Red blood cells (erythrocytes) are trapped in filaments of fibrin protein (pink fine fibers). The fibres of the absorbent material of the gauze are also seen (thicker fibers). When an injury occurs, platelets in the blood stimulate the formation of fibrin filaments, which enmesh platelets and red and white blood cells. The fibrin contracts around them to form a solid clot. Gauze is used to help stop bleeding, and to keep an injury clean and dry during healing or surgery. Magnification: x1000 when printed 10cm wide.