The outer cells become thin membranes that form around the baby.The cells multiply thousands of times and move to new positions to eventually become the embryo (pronounced: em-bree-o).

外层细胞发育成厚厚的膜并最终包裹着胚胎盘，细胞以成千上万的倍数增长并最终形成胚胎。

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The outer cells become thin membranes that form around the baby. The cells multiply thousands of times and move to new positions to eventually become the embryo (pronounced: em-bree-o).

外层细胞发育成厚厚的膜并最终包裹着胚胎盘，细胞以成千上万的倍数增长并最终形成胚胎。

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