During 1954-1961, a defect-centric paradigm gained prominence in crystallography and materials science, shifting from ideal lattice ideals toward a defect-based understanding of mechanical behavior and microstructure. The period highlights dislocations as primary carriers of plastic deformation and links between defect content and hardening, while early work connected lattice defects to vibrational spectra and irradiation effects, setting the stage for imaging-based defect assessment and improvements in crystal growth. Experimental demonstrations of defect visualization and strategies to minimize dislocations in crystal growth marked a trajectory toward electronics-grade materials.