Bone, while seemingly inert, is an active, growing, and changing part of the human body, in addition to being the body's primary calcium reservoir. In the correct homeostatic conditions, bone can remodel in response to damage, stress, or hormonal signaling (parathyroid hormone and calcitonin). Osteocytes located deep in the bone sense damage and signal bone-lining cells that will begin the process of remodeling. This process is vital not only for damage repair but also to adapt to a new environment and conditions.