Collagen is a long, fibrous structural protein. It is both the main protein of connective tissue in animals and the most abundant protein in mammals. Collagen can also be found in some cells and is one of the main components of cartilage, ligaments, tendons, bones, and teeth. It also helps give skin strength and elasticity. Collagen is very important to the body. It is often used in health and body care products to enhance well-being and to support the body.