Colloidal crystals, dense assemblies of micrometer-size particles in a solvent, are in many ways similar to their atomic counterparts: they have the same crystal structures, undergo the same phase transition, and possess the same crystal defects. In contrast to these structural properties, the mechanical properties of colloidal crystals are quite distinct from those of atomic systems. For example, unlike in atomic systems, the elasticity of hard-sphere colloidal crystals is purely entropic; as a result, they are so soft that they can be melted just by stirring. In this talk, I will show colloidal crystals exhibit work hardening. Remarkably, despite their softness, the shear strength of colloidal crystals can increase and approaches the theoretical limit, making them ‘stronger’ than most metals. By using confocal microscopy, we show the strength of colloidal crystals increases with dislocation density and ultimately follows the classic Taylor scaling behavior for atomic materials. The striking resemblance between colloidal and atomic crystals, despite the many orders of magnitude difference in particle size and shear modulus, demonstrates the universality of work hardening.