Healing of the bone is different with the other part of the body. Fracture healing is actually a bone regeneration with no scar tissues, where as in wound healing, injured tissue is replaced by connective tissue which became a scar, Traditionally fracture healing is divided in to 4 stages: 1) Stage of inflammation; 2) Stage of soft callus; 3) Stage of hard callus and 4) Stage of remodeling. In this article we reviewed each stage physiologically, histologically, histochemically and biochemically, although we discussed nutritional, mineral, stress and electrical factors in fracture healing and nonunions. In summary although fracture healing can be analysed discriptively but we still don not know, what is the inducting factor in fracture healing, and what are the factors to continue the process of fracture healing.