In 1980, a large-scale mutagenesis screen was carried out for the first time in an animal using Drosophila melanogaster and led to discovery of numerous important genes to create an animal body. However such a forward genetics approach had been thought to be difficult (impossible) in vertebrate. Dr. Nusslein-Volhard’s group challenged a large-scale screen for mutants affecting vertebrate development by employing zebrafish as a model vertebrate. The manuscript describes the success of the large-scale mutagenesis in zebrafish and I would like you to learn what factors need to be considered to make such an approach possible.