Novel nanostructured materials are the key to our transition toward a sustainable energy society. To achieve optimal material performance we need to understand the relationship between nanoscale structure/microstructure and material properties. Imperfections, such as structure defects, interfaces, multi-scale heterogeneities, and crystal architecture, tailor the materials' response to diverse chemical and mechanical environments. Our research focuses on the knowledge-based design of nanostructured materials for energy and environmental applications. We combine experimental with computational methods to enlighten atomic arrangement and dynamics in complex materials. We advance scattering/diffraction methods to bridge in-situ observations with multiscale simulations. We use experimental evidence to validate atomistic simulations. We use the unique perspective on materials properties and kinetics accessed by numerical methods to support the design of new nano-architectured materials.