The specific stage of mammalian embryonic development that precedes implantation, characterized by the formation of an inner cell mass.

医生建议将胚胎培养到囊胚阶段再进行植入。

An early stage of embryonic development in animals, typically consisting of a hollow sphere of cells.

囊胚是多细胞动物胚胎发育的一个早期阶段。