What is collagen? Collagen is an important adhesive protein present in our whole body. The name is derived from the Greek word κολλώ (Colla=glue) and also means to bind together. Our joints, bones, muscles, hair, nails, connective tissue and our skin are all made of collagen. So it plays an important role for many organs in our whole body! Our bodies produce collagen themselves, but after the age of 25 the production begins to decline.