This timely text covers the theory and practice of surface and nanostructure determination by low-energy electron diffraction (LEED) and surface X-ray diffraction (SXRD): it is the first book on such quantitative structure analysis in over 30 years. It provides a detailed description of the theory, including cutting-edge developments and tested experimental methods. The focus is on quantitative techniques, while the qualitative interpretation of the LEED pattern without quantitative I(V) analysis is also included. Topics covered include the future study of nanoparticles, quasicrystals, thermal parameters, disorder and modulations of surfaces with LEED, with introductory sections enabling the non-specialist to follow all the concepts and applications discussed. With numerous colour figures throughout, this text is ideal for undergraduate and graduate students and researchers, whether experimentalists or theorists, in the fields of surface science, nanoscience and related technologies. It can serve as a textbook for graduate-level courses of one or two semesters.