Mammalian development: New trick for an old dog Anthony Graham  Current Biology  Volume 10, Issue 11, Pages R401-R403 (June 2000) DOI: 10.1016/S0960-9822(00)00503-0

Figure 1 (a) Schematic diagram of a blastocyst — a 3.5 day mouse embryo. The locations of the inner cell mass and the trophectoderm are highlighted. (b) Schematic diagram of a 6.5 day mouse embryo during the early period of gastrulation. As gastrulation proceeds, the cells of the presumptive mesodermal cells of epiblast move to and through the primitive streak, shown by blue arrows. The primitive streak itself will also extend anteriorly, indicated by the red arrow, and at its anterior end the node will be established. Current Biology 2000 10, R401-R403DOI: (10.1016/S0960-9822(00)00503-0)