Imagine our body without bones and joints. Bones constitute about 15% of total body weight. Bone is a dynamic structure in a living body. It consists of multiple layers of fibers around which minerals such as calcium are deposited in crystalline form. The hardness and rigidity of bones are due to minerals, whereas resilience and toughness are due to fibers. Remodeling of bones (turnover) continues throughout life and is brought about by various bone cells. The remodeling cycle of bone is an orderly process initiated by osteoclasts (cells that destroy bone and form a 'pit') and followed by the formation of new bone by cells known as osteoblasts. Thus, bone formation and resorption are in dynamic equilibrium. Calcium is an essential constituent of bones. Vitamin D, formed under the skin on exposure to sunlight, maintains calcium balance and is essential in bone formation.