This tutorial will help you to understand how bone growth is different from the growth of many other organs. Although bone may appear to be rigid and lifeless it is actually living tissue that is capable of growth. Unlike soft tissues, bone cannot simply grow by adding additional cells and removing cells that are no longer necessary. The calcium laid down in bone gives the skeleton the strength and rigidity needed to protect and support the body. This rigidity means that expansion requires addition of cells on the outside and, when necessary, the removal of calcium and other materials on the inside.