Coloured scanning electron micrograph (SEM) of red blood cells (erythrocytes) trapped in a fibrin mesh (brown). The production of fibrin is triggered by cells called platelets; activated when a blood vessel is damaged. The fibrin binds the various blood cells together; forming a solid structure called a blood clot. A blood clot is a normal response; preventing an excessive loss of blood. http://footage.framepool.com/es/shot/298855542-fibrin-fisiolo...