By day 8 the cells are sorting and arranging themselves - the green fetal cells have condensed together, and in red here are the cells that will form the interface between the baby and the placenta.

到第 8 天， 细胞开始自行分类和排列 - 绿色的胎儿细胞已经凝聚在一起，红色的是将形成婴儿和胎盘之间界面的细胞。