ÌáÒª: Interfaces are common planar defects in solids. Interface can act as barriers, sinks and sources for other defects. By tailoring interface structures and properties, materials can be designed to achieve unusual properties, such as high strength, good ductility, high toughness, and high irradiation tolerance. To achieve this goal, multi-scale methods including experiment and theory and modeling are necessary. In this talk, I will present fundamental principles in developing interface-dominated composites, and the development of experimental techniques and materials modeling tools at different scales.