The skeletal system and the bone marrow immune system are not only physically adjacent but also regulate each other through precise molecular mechanisms. The interaction between the skeleton and the immune system, osteoimmunology, was first and best characterized in the molecular mechanism of osteoclastogenesis from monocytes. The most potent osteoclastogenic factor, RANKL, was first identified as a T cell factor. Subsequently, while the investigators tried to unravel the question of why osteoclasts exist only in bone while T cells are everywhere, the term osteoimmunology was coined by the group of Hiroshi Takayanagi and Professor Yongwon Choi, thereby opening the door to research in this field. Recently, osteoimmunology has been the focus of extensive research, centering on osteoclast biology, inflammatory bone diseases such as rheumatism/arthritis/periodontitis, and bone metastasis. For SSBH 2024, we invited three investigators who have recently made significant contributions to osteoimmunology. Notably, Professor Hiroyuki Okada from the University of Tokyo has developed a method to sequence the nuclei of osteoclasts separately, thereby revealing osteoclast biology with a unique approach in the era of single-cell transcriptomics. Prof. Okada gave a beautiful presentation at the last ASBMR, and we wanted to have an in-depth lecture and discussion. Professor Sungho Park from UNIST has been working on the epigenetic regulation mechanisms of rheumatoid arthritis after publishing a notable paper on the epigenetic regulation of osteoclasts, and he will update us on the latest research findings. Professor Je-Hwang Ryu from Chonnam National University College of Dentistry has recently published a paper on the role of cholesterol metabolism in the progression of periodontitis and will discuss this content and follow-up research.