This Research Topic comprises ten articles describing different approaches to study the regulation or maturation of bone marrow adiposity. The conversion of the "red" hematopoietic bone marrow to a "yellow" fatty one is a long-known phenomenon that has been referred to by many names. Bone Marrow Adipocytes (BMAds) have also been revealed as puzzling yet intriguing cells, which could provide exciting novel insights into the pathophysiology and treatment of aging, osteoporosis, anorexia nervosa, obesity and diabetes, aplastic anemia, multiple myeloma, leukemia, bone metastases, and many other clinical conditions. Thus, it is no wonder that enthusiasm surrounding Bone Marrow Adiposity (BMA) research has accelerated in recent years, especially since techniques for the isolation and study of BMAds have become increasingly refined and established (Figure 1). However, literature on the role of BMAds shows considerable variation and inconsistencies so far. The need for consensus and uniformity in this growing field of research is therefore a major issue that has been highlighted by the International Bone Marrow Adiposity Society (BMAS). BMAS was founded in 2017 to consolidate the growing scientific community interested in BMA, after the success of meetings organized since 2015. This young society brings together physicians and scientists working on rheumatology and bone biology, oncology, hematology, medical imaging, endocrinology, and metabolic perturbations, for which BMA research provides a new scientific direction. So far there have been five meetings with an excellent standard of keynote lectures and research presentations, in combination with interactive discussions in working groups. Reports from the third and the fourth meetings are presented in this Research Topic (Corsi et al.; Penel