<p>3D printing methods for small-scale metals enable a unique 10–100 nm dimensional niche where functional feature sizes, critical microstructural detail and atomic-level defects converge, challenging conventional hierarchical relationships and carrying significant nanomechanical implications. We introduce a metal nano-printing system combining two-photon lithography, hydrogel infusion-based additive manufacturing and in situ mechanical experiments on 3D nano-architected Ni, achieving ~100 nm critical dimensions, ~10 nm surface roughness, and a broad range of geometries (periodic vs. non-periodic; beam-based vs. shell-based) with superior specific strengths of ~100 MPa·g − 1·cm³ enabled by an unambiguous smaller is stronger size effect. Experiments identify concentrated-porosity regions as primary deformation-initiation sources and quantify their distribution as input for physics-informed, multiscale finite-element simulations that accurately predict size-dependent mechanical properties governed by nanoporosity-driven deformation. This work integrates experimental and computational approaches for the fabrication, characterization, and evaluation of nano- and micro-architected metals for nanotechnology and nanoscale manufacturing systems.</p>