Scientists from Seattle and Berlin have published an atlas on mouse embryonic development. In their study the researchers examined about two million cells, with the RNA of each cell labeled individually with a specially developed method termed sci-RNA-seq. They describe, which cell types differentiate between days 9.5 and 13.5 of mouse embryonic development, and how they transform into organs. In total, the scientists were able to identify 38 different main cell types and over 500 subtypes. In addition, they described 56 developmental trajectories in organ development for different cell types. The researchers compiled their results in an online atlas and made them accessible to the public.