Our bones are living tissue. They develop, grow, and have the ability to repair itself during injury. We are born with 300 bones, and as we grow old these bones become harder and fuse together, leaving the adult skeleton with 206 bones. Our bones are responsible for structural support and protection of vital organs. It also provides spaces where blood cells are produced and where minerals are stored. The ability of our bones to withstand stress is due to its protein framework made from collagen, and to its hard matrix made from calcium phosphate.