Inner Cell Mass Cells (ICM)

Just before the blastocyst implants into the uterine wall, the inner cell mass cells further diverge into epiblast and hypoblast layers. These cells are considered to be naive ground state omnipotent stem cells, with high clonogenicity, capability of forming chimeras and teratomas. These cells would typically have two activated X chromosomes in female embryos. The cells will eventually develop into two distinct cell types- epiblast and hypoblast cells giving rise to embryonic and extraembryonic structures, respectively.