The study of bones has attracted researchers from many medical fields. To understand bone-organ interactions, hematologists were challenged to investigate bone marrow (BM), the core of bone where hematopoiesis takes place. Through studies of the hematopoietic stem cells niche, hematologists contributed to the discovery of unexpected functions of bone-forming osteoblasts and bone-buried osteocytes. In particular, the recent findings about osteocytes, as the regulatory system of lympho-hematopoiesis and fat metabolism, highlighted the central role of skeletal tissue in inter-organ communication. The cross-cutting consideration including hematology and many other fields will expand the bone research.