translation.en: So, to begin with, however, I have to give you a very, very quick lesson in developmental biology, with apologies to those of you who know some biology.
translation.zh: 好的，可是一开始 我需要给你们上一个非常非常短的 有关生物生长的课程， 同时我对你们之中有生物知识背景的人表示歉意。