Volume 63 of Reviews in Mineralogy and Geochemistry provides an introduction for those not yet familiar with neutrons by describing basic features of neutrons and their interaction with matter as well illustrating important applications. The volume is divided into 17 Chapters. The first two chapters introduce properties of neutrons and neutron facilities, setting the stage for applications. Some applications rely on single crystals (Chapter 3) but mostly powders (Chapters 4-5) and bulk polycrystals (Chapters 15-16) are analyzed, at ambient conditions as well as low and high temperature and high pressure (Chapters 7-9). Characterization of magnetic structures remains a core application of neutron scattering (Chapter 6). The analysis of neutron data is not trivial and crystallographic methods have been modified to take account of the complexities, such as the Rietveld technique (Chapter 4) and the pair distribution function (Chapter 11). Information is not only obtained about solids but about liquids, melts and aqueous solutions as well (Chapters 11-13). In fact this field, approached with inelastic scattering (Chapter 10) and small angle scattering (Chapter 13) is opening unprecedented opportunities for earth sciences. Small angle scattering also contributes information about microstructures (Chapter 14). Neutron diffraction has become a favorite method to quantify residual stresses in deformed materials (Chapter 16) as well as preferred orientation patterns (Chapter 15). The volume concludes with a short introduction into neutron tomography and radiography that may well emerge as a principal application of neutron scattering in the future (Chapter 17).