The article "Circadian Regulation of Bone Remodeling" by Nobuaki Kikyo reviews the molecular and physiological mechanisms by which circadian rhythms influence bone remodeling. Bone remodeling is a continuous process involving the balance between bone resorption by osteoclasts and bone formation by osteoblasts. Circadian rhythms have been observed in serum and urine levels of bone turnover markers, such as digested collagen fragments and bone alkaline phosphatase, as well as in the expression of over 25% of transcripts in bones. Key genes involved in bone remodeling, including those encoding master transcription factors for osteoblastogenesis and osteoclastogenesis, osteogenic cytokines, and signaling pathway proteins, exhibit circadian rhythmicity. Serum levels of calcium, phosphate, parathyroid hormone, and calcitonin also show circadian patterns. Knockout mice targeting the core circadian regulator gene *Bmal1* exhibit disrupted bone remodeling, although results have not always been consistent. Despite these findings, establishing a direct link between circadian rhythms and bone remodeling in vivo remains challenging due to the difficulty in repeatedly collecting bone materials from human subjects and the differences in circadian gene regulation between diurnal humans and nocturnal mice. Understanding the circadian regulation of bone remodeling could reveal novel regulatory mechanisms underlying bone disorders such as osteoporosis, genetic diseases, and fracture healing. The article highlights the importance of further research using in vivo models, particularly mouse models, to bridge the gap between observed circadian-related changes in bone and the detailed molecular mechanisms involved in bone remodeling.The article "Circadian Regulation of Bone Remodeling" by Nobuaki Kikyo reviews the molecular and physiological mechanisms by which circadian rhythms influence bone remodeling. Bone remodeling is a continuous process involving the balance between bone resorption by osteoclasts and bone formation by osteoblasts. Circadian rhythms have been observed in serum and urine levels of bone turnover markers, such as digested collagen fragments and bone alkaline phosphatase, as well as in the expression of over 25% of transcripts in bones. Key genes involved in bone remodeling, including those encoding master transcription factors for osteoblastogenesis and osteoclastogenesis, osteogenic cytokines, and signaling pathway proteins, exhibit circadian rhythmicity. Serum levels of calcium, phosphate, parathyroid hormone, and calcitonin also show circadian patterns. Knockout mice targeting the core circadian regulator gene *Bmal1* exhibit disrupted bone remodeling, although results have not always been consistent. Despite these findings, establishing a direct link between circadian rhythms and bone remodeling in vivo remains challenging due to the difficulty in repeatedly collecting bone materials from human subjects and the differences in circadian gene regulation between diurnal humans and nocturnal mice. Understanding the circadian regulation of bone remodeling could reveal novel regulatory mechanisms underlying bone disorders such as osteoporosis, genetic diseases, and fracture healing. The article highlights the importance of further research using in vivo models, particularly mouse models, to bridge the gap between observed circadian-related changes in bone and the detailed molecular mechanisms involved in bone remodeling.