Apoptotic osteocytes might initiate bone remodeling by sending signals to lining cells, which retract from the bone surface to form a structure named the bone remodeling compartment (BRC). Osteoclast precursors are transported to the BRC by marrow capillaries, differentiate to mature osteoclasts under the influence of pro- and anti-osteoclastogenic cytokines (RANKL, M-CSF and OPG) derived from osteocytes, and initiate bone remodeling. Osteoblast precursors from the bone marrow or the circulation differentiate into mature, bone synthesizing cells in response to factors released from the bone matrix by resorption. Differentiation and function of osteoblasts is controlled by molecules derived from osteocytes, including sclerostin and Dkk1. (Reprinted with kind permission of Elsevier, Basic and Applied Bone Biology, Chapter 2 Bone Cells, Bellido, Plotkin and Bruzzaniti).