Dr Iyengar has built up at Trombay a group dealing with various aspects of neutron scattering completely based on locally designed and fabricated equipment. In this process, he has introduced widely recognized innovations in experimental techniques for neutron beam research and has made notable contributions to the basic understanding of vibrations of atoms in crystal lattices, internal motions of molecules and magnetic ordering and magnetic interactions in solids. He has promoted the growth of neutron crystallography and studies on the liquid state using neutrons. He is an acknowledged international authority on research reactor utilization.