Active crystals are highly ordered structures that emerge from the self-organization of motile objects, and have been widely studied in synthetic^1,2 and bacterial^3,4 active matter. Whether persistent crystalline order can emerge in groups of autonomously developing multicellular organisms is currently unknown. Here we show that swimming starfish embryos spontaneously assemble into chiral crystals that span thousands of spinning organisms and persist for tens of hours. Combining experiments, theory and simulations, we demonstrate that the formation, dynamics and dissolution of these living crystals are controlled by the hydrodynamic properties and the natural development of embryos. Remarkably, living chiral crystals exhibit self-sustained chiral oscillations as well as various unconventional deformation response behaviours recently predicted for odd elastic materials^5,6. Our results provide direct experimental evidence for how non-reciprocal interactions between autonomous multicellular components may facilitate non-equilibrium phases of chiral active matter.

活性晶体是从运动物体的自组织中出现的高度有序的结构，已在合成^1,2和细菌^{3,4中得到广泛研究}活性物。目前尚不清楚在自主发育的多细胞生物群体中是否会出现持久的晶体秩序。在这里，我们展示了游动的海星胚胎自发地组装成跨越数千个旋转生物体并持续数十小时的手性晶体。结合实验、理论和模拟，我们证明了这些活晶体的形成、动力学和溶解是由流体动力学特性和胚胎的自然发育控制的。值得注意的是，活的手性晶体表现出自持手性振荡以及最近预测的奇数弹性材料的各种非常规变形响应行为^5,6. 我们的结果为自主多细胞成分之间的非互惠相互作用如何促进手性活性物质的非平衡相提供了直接的实验证据。