Red blood cells (erythrocytes) in a fibrin mesh, coloured scanning electron micrograph (SEM). A blood clot is starting to form with many erythrocytes (red) becoming entangled in a fibrin mesh (tan). Erythrocytes transport oxygen from the lungs to the rest of the body and also remove carbon dioxide from the body by transporting it to the lungs where it is then exhaled. Fibrin is a protein formed from fibrinogen during the clotting of blood. The polymerised fibrin will help to form a clot over the wound. Magnification: x1025 when printed at 10cm wide.