Nature has evolved high-efficiency materials over many thousands of years which are among the most energy efficient, lightest, toughest and hardest known to man. However, commonly used materials have limited functionalities and inferior properties (dictated by their microstructure and thermo-mechanical properties; interfaces, grain boundaries, defects). Nanoscale structured composites, on the other hand, (e.g. nanolaminates, composite nanowires, and nanofoams), exhibit remarkable thermo-mechanical properties with excellent thermal stability and resistance to harsh environments. Materials science and engineering has made significant advances in understanding and identifying of the fundamental mechanisms that control the behavior of nanoscale structured materials: heterogeneity, interfacial topology and chemistry, self-assembly, and functionality. By harvesting and building on these recent advances in nanomaterial science and engineering, we have the opportunity to design new materials for energy efficiency and high energy environments. In this presentation, I will discuss our activities and achievements in this area, and will elucidate on scientific challenges and opportunities.