Gastrulation n. : The process of invagination, in embryonic development, by which a gastrula is formed.

Example:
It is sometimes said that the most important event in a human life is Gastrulation.?

Taxonomy
cells, gastrulation, embryo, blastocoel, hypoblast, archenteron, yolk, endoderm, mesoderm, layers, ectoderm, blastoderm, vegetal pole, epiboly, dorsal, EVL, YSL, mesenchyme cells.

Defination from the web:
Gastrulation is a phase early in the development of most animal embryos, during which the morphology of the embryo is dramatically restructured by cell migration. ... In humans, gastrulation occurs after implantation, around days 14-16 after fertilization in human embryogenesis. ...