Stephane Nedelec and colleagues have developed an in vitro system to recapitulate human trunk axis formation. “The idea was to use the limitations of in vitro models to probe for the mechanisms and constraints that control patterning and morphogenesis during human embryogenesis,” says Nedelec. They thought that, since neurogenesis is induced by the inhibition of transforming growth factor (TGF)-β and bone morphogenetic protein (BMP) signaling pathways, these factors might also be suppressing axial progenitor-like cells. Thus, they treated human induced pluripotent stem cells (hiPSCs) with a Wnt agonist in the absence of a TGF-β or BMP inhibitor. These cells broke symmetry by day four and morphed into an elongated shape.