The article discusses a research on the role of osteoclasts in mediating hematopoietic stem cell mobilization. It references a study by O. Kollet and colleagues in this same issue. It has been observed that RANK ligand increased osteoclastogenesis and that osteoclastogenesis was accompanied by stem and progenitor cell mobilization. RANK also decreased the abundance of osteoblast kit ligand and the production of osteopontin.