Professor Watts has made outstanding contributions to fields as disparate as liquid state theory, collisional energy transfer and sputtering dynamics. He was the first to show that integral equation methods are capable of describing the gas-liquid coexistence curve. He was one of the first to develop intermolecular potential surfaces of spectroscopic accuracy. With Barker he developed the benchmark argon potential; he developed models for water, benzene, ammonia and methane. These models account for the thermodynamic, transport and spectroscopic properties in all three phases. Watts has exploited state-selected, crossed beam experimental methods to refine interintramolecular potential functions and dynamics.