Bone is essential for human health and wellbeing due to its central role in the musculoskeletal system. Bone is continually remodeled to maintain bone performance. At the border between old and new bone, cement lines occur. Cement lines are only a few microns across and their composition differs from that of the surrounding bone. However, their structure remains unknown. This information is important for understanding both bone mechanical properties and the signals that govern the behavior of bone cells involved in bone remodeling. Since bone is a 3D composite, the structure must be mapped in 3D. This has recently become possibly by new techniques developed by the proposers. We thus propose to conduct combined SAXS tensor and texture tomography to map the orientation distributions of, respectively, nanostructural features and the bone biomineral nanocrystals. This will enable forming a structural model of cement lines for the first time.