During development of the embryo it goes from being a single cell, the fertilized egg, to being a multi-cellular organism with billions of cells in it.

胚胎的发育,始于一个单一细胞,即受精卵,直到形成一个以十亿计数量的细胞构成的,多细胞有机体

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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。

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