Interfaces are integral parts of composite materials and can significantly affect their physical properties. In biological systems, molecules at the interfaces regulate mineral formation or mitigate structural mismatch of the organic and inorganic moieties to provide optimal mechanical properties. In energy storage systems, most transport, degradation, and safety issues derive from processes at interfaces. However, due to the intrinsic nature of interfaces, i.e., being “buried” and disordered, non-destructive investigation to obtain insights into the compositions and structures of interfaces can be challenging. Research in our group will involve characterizing the interfacial structures of composite materials with multinuclear high-resolution solid-state nuclear magnetic resonance (NMR) complemented by microscopy and X-ray/neutron based techniques. By understanding the structure-property relationships and designing stable and active interfaces via surface engineering, we seek to improve the performances of technologically important materials.