 From 1985 to 1987 he was a Visiting Research Associate at Cornell University and then from 1989 to 1991 at the ESPCI ParisTech in Paris.He was a professor of physics at Princeton University, becoming a Professor in the Department of Molecular Biology in 1993.He was an Investigator at Howard Hughes Medical Institute (2000–2001), and Tri-Institutional Professor at the Weill Cornell Medical College and the Sloan-Kettering Institute (2003–2010).