Blood clot crystals. Coloured scanning electron micrograph (SEM) of crystals of albumin from a blood clot. Albumin is the most abundant protein in the blood plasma. When the skin is cut, small blood vessels are ruptured, releasing blood. Some proteins in the blood plasma (such as albumin) harden in the air to form crystals (pink) 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's other roles in the blood include helping to maintain the levels of hormones and calcium, and assisting water flow between the bloodstream and body tissues.