REGULATOR is a metazoan transcription factor (TF) and maternal factor resource, specifically designed for developmental biology studies. Maternal factors were expressed in unfertilized eggs, and gradually reduced as time goes on. In order to reduce the search space of developmentally important genes, we only focused on those specifically expressed genes in egg stages, whose expression value ≥ 8 times than the mean value of others. There are ~77 metazoan species in the current database. The identification of TFs was based on statistical information similarity of protein features.