Embryonic tissues develop during the stage.

Embryonic tissues or germ layers develop during the gastrulation stage. Gastrulation is a process in embryonic development during which the single-layered blastula is reorganized into a three-layered(or two-layered) structure called the gastrula. Two primary germ layers(embryonic tissues) are an inner layer-endoderm and an outer layer-ectoderm. Endoderm and ectoderm interact and produce a third layer-mesoderm. Gastrulation is followed by organogenesis, three germ layers will give rise to specific tissue and organ.For example, ectoderm gives rise to epidermis and nervous system, endoderm to the digestive system and mesoderm to muscles, bones…

They must use the scientific method