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Gastrulation is a critical process during week 3 of human development. Gastrulation is an early developmental process in which an embryo transforms from a one-dimensional layer of epithelial cells, a blastula, and reorganizes into a multilayered and multidimensional structure called the gastrula. In triploblastic organisms such as reptiles, avians, and mammals, gastrulation attains a three tissue-layered organism composed of endoderm, mesoderm, and ectoderm. Each germ layer corresponds to the development of specific primitive systems during organogenesis. In addition to setting the embryo up for organ formation, gastrulation provides a mechanism to develop a multileveled body plan that demarcates anatomical axis formation. These axes are the dorsal/ventral axis, also termed the anterior/posterior or rostral/posterior axis, and the cranial/caudal or superior/inferior axis. Gastrulation also promotes the retention of global left and right symmetry and the loss of bilateral symmetry in specific organs such as the heart.