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...