translation.en: It's not like your heart cells and your kidney cells get all mixed up every day, and that's because there's all of this chemistry going on, these molecules that say who each of these groups of cells is, and what their tasks should be.
translation.zh: 你们的心脏和肾脏细胞不会每天混杂在一起， 这是因为你体内有一大堆化学反应不断地进行着， 这些分子能够区分不同的细胞群组， 还有它们所应该执行的任务。