“…First, we performed a comparative analysis of gene regulation during development in seven species with varying evolutionary distances at single-cell resolution. Development atlases of four invertebrates and three vertebrates were involved, including Schmidtea mediterranea 12 , Caenorhabditis elegan 15 , Ciona intestinalis 16 , Hydra vulgaris 13 , Danio rerio 42 , Mus musculus 11 , and Homo sapiens 14 . More than 1,100,000 cells were collected and categorized into 665 cell type pairs for relatively differentiated states and undifferentiated states (Extended Data Fig.…”