Albumin crystals. Coloured scanning electron micrograph (SEM) of crystals of albumin outside a wound. Albumin is the most abundant protein in the blood plasma. When the skin is cut, small blood vessels are ruptured, releasing blood onto the epidermis (pink). Some proteins in the blood plasma harden in the air to form crystals (green) over the wound. Other blood proteins then help form a clot over the wound, preventing excessive blood loss, and keeping the wound free of bacteria and other foreign bodies. Albumin in the blood helps maintain the levels of hormones and calcium, and also assists water flow between tissues and the bloodstream. Magnification unknown.