The aim of the present book is to describe the current state of the art of application of neutron scattering techniques in those scientific areas that are most active. The presentation is aimed primarily at professionals in different scientific disciplines, from graduate students to research scientists and university faculty members, who may be insufficiently aware of the range of opportunities provided by the neutron technique in their area of specialty. It does not present a systematic development of the theory, which may be found in excellent textbooks such as those of Lovesey or Squires, or a detailed hands-on manual of experimental methods, which in our opinion is best obtained directly from experienced practitioners at the neutron centers. It is rather our hope that this book will enable researchers in a particular area to identify aspects of their work in which the neutron scattering technique might contribute, conceive the important experiments to be done, assess what is required to carry them out, write a successful proposal for this purpose for one of the centralized user facilities, and carry out the experiments under the care and guidance of the appropriate instrument scientist. With this object in view, each chapter relating to a particular field of science has been written by a leading practitioner or practitioners of the application of the neutron methods in that field.