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Abstract Magnesium, the lightest structural metal, usually exhibits limited ambient plasticity when compressed along its crystallographic c -axis (the “hard” orientation of magnesium). Here we report large plasticity in c -axis compression of submicron magnesium single crystal achieved by a dual-stage deformation. We show that when the plastic flow gradually strain-hardens the magnesium crystal to gigapascal level, at which point dislocation mediated plasticity is nearly exhausted, the sample instantly pancakes without fracture, accompanying a conversion of the initial single crystal into multiple grains that roughly share a common rotation axis. Atomic-scale characterization, crystallographic analyses and molecular dynamics simulations indicate that the new grains can form via transformation of pyramidal to basal planes. We categorize this grain formation as “deformation graining”. The formation of new grains rejuvenates massive dislocation slip and deformation twinning to enable large plastic strains. 

Single crystal perovskite microplates are fundamentally and technologically very important to developing high‐order (n≥ 3) multiphoton excitation. This study reports the preparation of high‐quality single crystal perovskite microplates through the controlled release of lead ions from the confined species within a metal–organic framework. The resulting free‐standing MAPbBr₃(MA = CH₃NH₃⁺) and CsPbBr₃single crystals of rectangular microplates exhibit excellent multiphoton excitation behaviors, as demonstrated in their five‐photon‐excited photoluminescence and three‐photon‐pumped stimulated emission with the threshold of 159 mJ cm⁻², providing the promise of exploring high‐quality single crystal perovskite microplates for functional optoelectronic and photonics applications.