Robert Thomas is renowned for his application of neutron and X-ray scattering methods to problems in physical chemistry, and in particular, the development of the grazing incidence reflection technique and its application to the study of wet interfaces. Wet interfaces are the surfaces separating air–liquid, liquid–liquid, and solid–liquid phases and, although they are of considerable fundamental and technological importance, were poorly understood because of an almost total lack of experimental techniques for investigating them at the molecular level. In 1981, Robert was the first to propose that neutron reflection be applied to the study of adsorption, and he has subsequently developed the experimental technique and its analysis to a point where it gives uniquely detailed information about molecular structure at wet interfaces. He was the first to apply it to the air–liquid and solid–liquid interfaces and he has been able to reveal the structure of a variety of amphiphilic molecules and polymers at these two interfaces.