In this book, I will present a number of techniques for analysis of powder diffraction data, concentrating on most, but not all, of the capabilities offered within the GSAS-II software package. I will devote the most attention to Rietveld analysis, which is a method for the determination of the arrangement of atoms in materials from a powder diffraction pattern, or as this process is commonly called, determination of the crystal structure. As will be seen, Rietveld analysis can be used for much more than crystal structure determination.