The cells of this surrounding sheet have become different in some way and they develop into the placenta and the extra embryonic tissues.

环抱在周围的这一层细胞,已经开始逐渐分化,最终成为胎盘,及额外的胚胎组织

耶鲁公开课 - 生物医学工程探索课程节选

It's this group of cells, this subset of cells from the developing embryo that become the embryo, that become the organism, become the human.

这一组细胞,这组发育胚胎中的细胞亚群,发育成胚胎,发育组织,直至发育成整个人体

耶鲁公开课 - 生物医学工程探索课程节选