With the head upright, take hold of the outer part of the ear.

VOA: special.2010.03.31

We can see the early signs of ear development Start with the thickening of the outer layer of the embryo, this layer is called the ectoderm.

大家知道，耳朵发育的早期特征,是胚胎外层膜的增厚，这层膜也叫外胚层。

斯坦福公开课 - 7个颠覆你思想的演讲课程节选

We can see the early signs of ear development Start with the thickening of the outer layer of the embryo, this layer is called the ectoderm.

大家知道，耳朵发育的早期特征,是胚胎外层膜的增厚，这层膜也叫外胚层。

斯坦福公开课 - 7个颠覆你思想的演讲课程节选