This important book presents a comprehensive account of the techniques and applications of single crystal neutron diffraction in the area of chemical crystallography and molecular structure. Beginning with a brief description of the general principles and the reasons for choosing the technique -- the "why" -- the book covers the methods for both the production of neutrons and the measurement of their scattering by molecular crystals -- the "how" -- followed by a detailed survey of past, present and future applications -- the "what". The coverage of both steady state and pulsed neutron sources and instrumentation is extensive, while the survey of applications is the most comprehensive yet undertaken. The book endeavours to show why the technique is an essential method for studying areas as diverse as hydrogen bonding and weak interactions, organometallics, supramolecular chemistry and crystal engineering, metal hydrides, charge density and pharmaceuticals. It is an ideal reference source for the research worker interested in using neutron diffraction to study the structure of molecules.