Collagen is not only most common protein of human body (and all vertebrates in general) with 30% to 48% participation in total protein weight but also, due to its' functions in an organism, the most crucial protein! This almost "miraculous" protein occurs in nearly every parts of the human body, from eyeballs, through bones, hair, nails, up to skin (in the latter collagen is 70% of all proteins). We want You to remember about one, vital thing - collagen is not given once for all - as all of our body it undergoes the continual process of exchange. Old one dies and is replaced and maintained by a system of cells called keratinocytes, chondrocytes and fibroblasts - cells that are specialised in collagen production.