As soon as you scrape or break the skin anywhere on your body, special blood cells called platelets get to work. Platelets stick together like glue at the cut site, forming a clot. This clot is like a protective bandage over your cut that keeps more blood and other fluids from flowing out. The clot is also full of other blood cells and thread-like matter called fibrin that help hold the clot together. As the clot starts to get hard and dries out, a scab forms. Crusty and dark red or brown, the scab protects the cut by keeping germs out and giving the skin cells underneath a chance to heal. All by itself, usually after a week or two, a scab falls off, revealing new skin underneath.