My research in elementary particle physics has been dominated by my work on string theory, with my first paper on that subject written in 1968. More recent research has addressed two major topics. First is the understanding of closed string states (including gravitons) as they appear in an open string theory, emphasizing the off-shell and gauge properties. The second topic is the Green-Schwarz string in a curved superspace background. We showed that symmetries required for the consistency of the superstring impose conditions on the background super-space-time which are equivalent to the supergravity equations of motion. It also gives a new picture of the “conventional supergravity constraints”, showing that the essential physics of supergravity is just what the string can feel.