A free online database of image and phenotype data for embryonic lethal knockout mice. The data sheds new light on genes that are critical for embryo development and survival. High-resolution 3D image analysis and tissue histology is used to identify abnormalities in both embryos and placentas from embryonic lethal lines. The data is searchable by gene or phenotype, all full-resolution images are available and phenotypes are annotated on the relevant images. Phenotype penetrance data is available for each line. The database also includes gene expression profiles for embryos from knockout lines.