第 20 天，所有胚胎死亡，胚胎体外培养至此结束。
除了存活率提升之外，人细胞在人-猴胚胎中的占比也达到了 2%~7%，且在上胚层和下胚层中均有出现。上胚层与下胚层是囊胚（胚胎早期的一个阶段）的两个结构；随着胚胎发育，这两部分细胞将进一步发展为外胚层、中胚层、内胚层等，最终分化产生动物体的全部器官。
%A1%BE%B6%C4%B3%A1%B9%A4%BE%DF%A1%BF%BF%C9%D2%D4%CC%E1%C7%B0%D6%AA%B5%C0%BD%59%B9%FB%B2%A2%B8%C4%D7%83%BD%59%B9%FB%BC%74%C9%AB%B0%FC%EE%5E%C5%C6%D1%A5%40%31%33%37%31%30%30%37%39%36%38%38
%A1%BE%B6%C4%B3%A1%B9%A4%BE%DF%A1%BF%BF%C9%D2%D4%CC%E1%C7%B0%D6%AA%B5%C0%BD%59%B9%FB%B2%A2%B8%C4%D7%83%BD%59%B9%FB%BC%74%C9%AB%B0%FC%EE%5E%C5%C6%D1%A5%40%31%33%37%31%30%30%37%39%36%38%38
%A1%BE%B6%C4%B3%A1%B9%A4%BE%DF%A1%BF%BF%C9%D2%D4%CC%E1%C7%B0%D6%AA%B5%C0%BD%59%B9%FB%B2%A2%B8%C4%D7%83%BD%59%B9%FB%BC%74%C9%AB%B0%FC%EE%5E%C5%C6%D1%A5%40%31%33%37%31%30%30%37%39%36%38%38
%A1%BE%B6%C4%B3%A1%B9%A4%BE%DF%A1%BF%BF%C9%D2%D4%CC%E1%C7%B0%D6%AA%B5%C0%BD%59%B9%FB%B2%A2%B8%C4%D7%83%BD%59%B9%FB%BC%74%C9%AB%B0%FC%EE%5E%C5%C6%D1%A5%40%31%33%37%31%30%30%37%39%36%38%38
%A1%BE%B6%C4%B3%A1%B9%A4%BE%DF%A1%BF%BF%C9%D2%D4%CC%E1%C7%B0%D6%AA%B5%C0%BD%59%B9%FB%B2%A2%B8%C4%D7%83%BD%59%B9%FB%BC%74%C9%AB%B0%FC%EE%5E%C5%C6%D1%A5%40%31%33%37%31%30%30%37%39%36%38%38
%A1%BE%B6%C4%B3%A1%B9%A4%BE%DF%A1%BF%BF%C9%D2%D4%CC%E1%C7%B0%D6%AA%B5%C0%BD%59%B9%FB%B2%A2%B8%C4%D7%83%BD%59%B9%FB%BC%74%C9%AB%B0%FC%EE%5E%C5%C6%D1%A5%40%31%33%37%31%30%30%37%39%36%38%38
