Thanks to high-throughput single-cell RNA sequencing (scRNA-seq), it is possible to construct single-cell transcriptomic atlases at the organic level. For example, cell atlases for vertebrate and invertebrate systems have been successfully generated, such as the Human Cell Landscape (HSC), Mouse Cell Atlas (MCA), Zebrafish Cell Landscape (ZCL) and Drosophila embryo. However, most of these studies are limited to one specific species or period and thus fail to make a thorough comparison between different species and tissues.