Why do early embryos divide into many smaller cells before increasing in overall size?

Early embryos divide into many smaller cells, a process known as cleavage, primarily to transform a single, relatively enormous zygote into a multicellular organism composed of cells of a more conventional, functional size.12

During this stage, there is almost no overall growth; instead, the total volume of living matter remains substantially unchanged as the zygote subdivides into smaller cells called blastomeres. This rapid series of mitotic divisions serves several critical purposes:12

• Building Units: It creates the necessary cellular building blocks for the future organism.2
• Cytoplasmic Distribution: It allows for the partitioning of the egg's [cytoplasm], which contains regulatory substances known as cytoplasmic determinants. These determinants help establish different cell populations that become committed to specific developmental fates.3
• Structural Organization: The process facilitates the formation of a blastula, a hollow ball of cells, which provides the structural foundation for subsequent developmental stages like rearrangement and differentiation.12

Essentially, cleavage converts a single, oversized cell into a manageable, multicellular cluster without requiring the energy-intensive process of increasing total biomass.12