Active cell divisions generate fourfold orientationally ordered phase in living tissue

Abstract Morphogenesis, the process through which genes generate form, establishes tissue-scale order as a template for constructing complex shapes of body plan. The extensive growth required to build these ordered substrates is fuelled by cell proliferation, which, naively, should destroy order. Understanding how active morphogenetic mechanisms couple cellular and mechanical processes order—rather than annihilate it—remains an outstanding question in animal development. We show that divisions are primary drivers tissue flow, leading fourfold orientationally phase. Waves anisotropic proliferation propagate across embryo with precise patterning. Defects introduced into nascent lattice moved out bulk towards boundary subsequent divisions. Specific rates orientations enable organize rather fluidize tissue. observe this using live imaging cartography analyse dynamics ordering trunk segmental ectoderm crustacean Parhyale hawaiensis beginning 72 h after egg lay. result robust, mechanism generating global orientational non-equilibrium system sets stage development shape form.