Scattering, diffraction, spectroscopy, and imaging techniques developed at electron accelerator based X-ray light sources during the last two decades have been highly effective in exploring the properties of various complex materials including a variety of interfaces at desired length, depth, time and energy scales. These methods have allowed to go beyond periodic systems and equilibrium structures and to obtain unprecedented insight into the relations between synthesis, processing, structure, and functional properties, especially by in situ studies during processing and/or under real working conditions of temperature, environment and magnetic or electric fields.