Neutron crystallography – Then and now *

Neutron crystallography began to be employed at the Bhabha Atomic Research Centre (BARC), Trombay, Mumbai in the early sixties. At that time, the technique, at BARC as well as elsewhere, was in a nascent state, with emphasis on building of instruments and development of crystallography software. Over the years, the Trombay group kept pace with the advancements in other parts of world and employed neutron diffraction to get answers to a variety of important problems. Here we review the advances of the method over the years and its applications. In particular, we discuss the phase problem in neutron crystallography and its contributions for hydrogen bonding, biological macromolecular structures and high pressure science.