This is an excellent site that will make researchers who study mice jump for joy (and just might make researchers who choose other model organisms a bit envious). The Edinburgh Mouse Atlas Project offers many tools for researchers, divided into the 3-D embryo anatomy atlas and the EMAGE gene-expression database. The embryo anatomy atlas does offer three dimensions (as promised), as one can move through transverse, frontal, or sagittal slices of embryos at different developmental stages, as well as watch animations of a complete embryo. The EMAGE database provides in situ hybridization gene-expression data in the embryo across developmental time. One can search by gene name, anatomy, or embryo space (a neat tool in which you color an area of the embryo and search for any genes that have expression within that region). Additionally (if I haven’t yet convinced you to visit the site), you can request CDs of the mouse atlas data, free of charge for academic use.