The importance of the characterization of microscale texture and grain boundary microstructures is discussed as basic knowledge of grain boundary engineering for advanced structural and functional polycrystalline materials. Some examples of recent success of grain boundary engineering for the control of brittle fracture in molybdenum and development of superplasticity in Al-Li alloy are introduced. Most recent challenges to grain boundary engineering for ferromagnetic materials through the application of magnetic field and for nanocrystalline materials are shown to be useful and powerful for future materials design and development.