*Establishes 3 germ layers (ectoderm, mesoderm, endoderm) *Establishes axes of embryo. *Cell specification. **Gastrulation is the first major morphogenetic transformation in embryonic development. In the frog, the process of gastrulation must accomplish two major goals: the closure of the blastopore to bring the endoderm and mesoderm fully inside the ectoderm, and the generation of the archenteron.