+The **blastula** is a hollow sphere of cells, a key early stage in [Embryo](/wiki/embryo) development. Formed after the [Morula](/wiki/morula), it encloses a fluid-filled cavity, the blastocoel, paving the way for further cellular organization.
+## See also
+- [Gastrula](/wiki/gastrula)
+- [Zygote](/wiki/zygote)
+- [Cleavage](/wiki/cleavage)
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