This selected article represents an outstanding breakthrough in the knowledge of primate/human embryo development. The authors have managed to culture and maintain primate embryos for up to 20 days for the first time. All previous knowledge on early mammalian embryo development (“gastrulation” phase) have been derived from murine studies. Further advances were made in primate models but during the first days (no longer than 14 days), not knowing about molecular mechanisms which govern gastrulation. In this work, the authors have used the human embryo culture protocol with cynomolgus monkey embryos up to 20 days. With advanced sequencing techniques (scRNA-seq and scATAC-seq), new insights are provided related to embryonic and extra-embryonic lineage segregation, bi-laminar disc germination, amniotic and yolk sac cavitation and primordial germ cell-like specification. The molecular signalling pathways of those are described, representing novel mechanistic insights of primate embryogenesis (specifically during gastrulation, the most important step of mammalian development after implantation), which in turn will help us to better understand and study human embryogenesis.