Designed for the undergraduate and postgraduate students of physics, materials science and metallurgical engineering, this text explains the theory of X-ray diffraction starting from diffraction by an electron to that by an atom, a crystal, and finally ending with a diffraction by a conglomerate of atoms either in the single crystal or in the polycrystal stage. This Second Edition of the book includes a new chapter on Electron Diffraction as electron diffraction along with X-ray diffraction are complementary to each other and are also included in the curriculum. The book amply blends the theory with major applications of X-ray diffraction, including those of direct analysis of lattice defects by X-ray topography, orientation texture analysis, chemical analysis by diffraction as well as by fluorescence. KEY FEATURES : Set of numerical problems along with solutions Details of some different experimental techniques Unsolved problems and Review Questions to grasp the concepts.