 A key early discovery was of homeotic genes that regulate development in a wide range of eukaryotes.The field is characterised by some key concepts which took evolutionary biologists by surprise.One is deep homology, the finding that dissimilar organs such as the eyes of insects, vertebrates and cephalopod molluscs, long thought to have evolved separately, are controlled by similar genes such as "pax-6", from the evo-devo gene toolkit.