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Metal microarchitectures with 3-dimensional solid frames can exhibit mechanical performance coming from the geometrical effect and characteristic size effect of material under dynamic and extreme temperature conditions. In this study, for the first time, full-metal Cu microlattices were fabricated via localized electrodeposition in liquid (LEL) process which enables high-precision additive manufacturing of metal at micro-scale. The microlattices possess a unique microstructure with micron sized grains that are rich with randomly oriented growth twins. They also have smooth surfaces and near-ideal nodal connectivity. Furthermore, Cu microlattices exhibited unique temperature (-150 and 25 Celcius degrees) and strain rate (0.001-100 s-1) dependent deformation behavior during in situ micromechanical testing. Systematic compression test of fully dense Cu micropillars, equivalent in diameter and length to the strut of microlattice at comparable extreme loading conditions, and post-mortem microstructural analysis revealed substantial shifts in deformation mechanisms depending on the temperature and strain rate. On one hand, at room temperature (25 Celcius degree), dislocation slip based plastic deformation occurs and leads to localized deformation of micropillars. On the other hand, at cryogenic temperature (-150 Celcius degree), mechanical twinning occurs and leads to relatively homogeneous deformation of micropillars. Based on the intrinsic deformation mechanisms at the component level, the temperature and strain rate dependent deformation behavior of microlattices is explained. Our findings provide valuable insights into the intricate …