Damage to tissue, such as a cut in the skin, begins to heal with the formation of a sticky lump known as a blood clot. Blood clots prevent blood and other fluids from leaking out. Microscopic sticky threads of the clotting protein fibrin make a tangled mesh that traps blood cells. Within a short time the clot begins to take shape, harden, and become more solid. The clot turns into a scab as it dries and hardens. Skin cells beneath the scab multiply to repair the damage. When the scab falls off the wound will be healed.