Online knowledge of genes involved in mouse kidney development is available from the literature (PubMed) and text-based (Kidney Development and Mouse Gene Expression-GXD) databases. Further information is in gene databases of other organisms having tissues homologous to the metanephros (e.g. Drosophila Malpighian tubules; tools are available for identifying mouse homologues of non-mouse genes) and from tissues homologous to those in the developing kidney (e.g. mesothelium that, like nephrons, arises from a mesenchyme to epithelial transition). Future databases will also include graphical data, and this knowledge will provide a further level of insight. These databases and tools are discussed here.