The rapid development of synthesis and characterization of materials with feature sizes at nanoscale as well as unprecedented computational power have brought forth a new era of materials research in which experiments, modeling and simulations are performed side by side to probe the unique mechanical properties of nanostructured materials. The purpose of this talk is to explore mechanics of nanotwinned materials which have been simultaneously fabricated in laboratories and discovered in nature. These materials appear to transcend the limits of conventional material systems by exhibiting an exceptional combination of superior strength and resistance to fracture, fatigue, and wear. A systematic study of these materials will almost certainly push the frontiers of structural materials for applications ranging from aerospace to automotive to biomedical devices.