A fractured bone bleeds. Bone repair begins, as over a period of hours blood at the fracture site clots and forms a hematoma. The healing begins as osteoclasts in the area remove dead bone tissue, while fibroblasts penetrate the area and build a fibrocartilaginous callus that bridges the broken bone. Over many weeks osteoblasts transform the callus into bone. Continued remodeling and the mechanical stress put on the bone creates and shapes new bone. Over a period of months or years the bone regains its original strength, shape, and internal structure.