At the present time, the laboratory mouse has become a central tool for skeletal studies, mainly because of the extensive use of genetic manipulations in this species. Naturally, this widespread use of mice in developmental, bone, joint, tooth, and neurological research calls for detailed anatomical knowledge of the mouse skeleton as a reference for experimental design and phenotyping under a variety of experimental conditions, including genetic manipulations (e.g., transgenic and kno- out mice). Several general treatises on the normal anatomy of the mouse and rat have been published in the previous century. In the absence of adequate technologies, these books describe only the external anatomical features of the different parts of the skeleton. In general, images in these atlases are camera lucida-based line drawings rather than accurate three-dimensional images. Furthermore, so far a systematic two- and three-dimensional description of the internal anatomy of bones, as well as the three-dimensional relationship exhibited in joints, are not available.