There are three types of bone cells. Osteoclasts, Osteoblasts, and Osteocytes. Osteoblasts are bone cells that use collagen and protein to form new bone if it is needed. Osteoclasts come from bone marrow and are large cells that dissolve bone. Osteocytes are cells found on the inside of bones. Osteocytes can sense if there is a crack in the bone and then be surrounded by new bone as it heals.