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Fig. 7 An overview of strategies for constructing gastruloids An “anterior-gastruloid” can be generated by applying a regional Nodal gradient in a group of naive cells (the animal pole explants of zebrafish in this work, upper). This gastruloid contains mainly the axial mesoderm (red region) and neural ectoderm (blue region) and further developed into an “HLS” structure with FB, MB, and HB, which was mapped to a representative vertebrate embryo. While under the activation of a BMP4 signaling center7 or exogenous WNT signaling,6,8,63 aggregates of pluripotent cells can develop into a “posterior-gastruloid,” which mainly comprises the tissues of trunk and tail region (“TLS,” bottom). Black arrow within “anterior-gastruloid” indicates involution movements (Inv) of mesendoderm, and curved two-headed arrows indicate the convergence and extension (C and E) movements in both kinds of gastruloid.