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ectoderm formation
endoderm formation
mesoderm formation
gastrulation
biological_process
A complex and coordinated series of cellular movements that occurs at the end of cleavage during embryonic development of most animals. The details of gastrulation vary from species to species, but usually result in the formation of the three primary germ layers, ectoderm, mesoderm and endoderm.
Wikipedia:Gastrulation
GO:0007369
embryonic morphogenesis