Collagen is a type of protein. Fibrous in nature, it connects and supports other bodily tissues, such as skin, bone, tendons , muscles, and cartilage . It also supports the internal organs and is even present in teeth. There are more than 25 types of collagens that naturally occur in the body. Collagen is one of the most plentiful proteins present in the bodies of mammals , including humans. In fact, it makes up about 25 percent of the total amount of proteins in the body. Some people refer to collagen as the glue that holds the body together. Without it, the body would, quite literally, fall apart. Possessing great tensile strength, collagen functions in a manner that is very different from many other types of proteins. For example, it can be found both inside and outside of cells. Collagen fibers are important in contributing to the external structure of cells. However, they are present on the inside of some cells as well. Collagen works hand-in-hand with elastin in supporting the b