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How does a morula become a blastocyst during early human development?

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Fetal growth — human development Growth of the human fetus from the fourth month to the ninth month of pregnancy.

During early human development, the morula—a solid, berrylike cluster of cells—transforms into a blastocyst through a process of fluid accumulation and cellular differentiation.12

As the number of cells in the morula increases (typically reaching around 30 or more), small pools of clear fluid begin to collect between the internal cells. These spaces eventually coalesce to form a single, subcentral, fluid-filled cavity known as the blastocoel.12

This transition marks the emergence of two distinct, differentiated cell types:2
* Inner Cell Mass: An eccentric cluster of cells that will eventually develop into the embryo.12
* Trophoblast: The external layer of smaller cells enveloping the inner mass, which will contribute to the formation of the placenta and fetal membranes.12

Once this hollow, bubblelike structure is formed, it is officially termed a blastocyst. During its time in the uterus, the blastocyst sheds its protective gelatinous capsule (the zona pellucida), expands in size, and prepares to attach to the uterine lining for implantation.134