His research focuses on understanding nucleon and nuclear structure using the lepton probe, frequently using spin observables and polarized internal gas targets. He has proposed and led experiments at SLAC, IUCF, MIT, DESY, and Jefferson Lab. He has served on numerous international advisory committees, was chair of the Division of Nuclear Physics of the American Physical Society (APS) in 2007, and served as chair of the International Spin Physics Committee from 2014 to 2017. He is a fellow of the APS, a recipient of a D.Sc. (honoris causa) from the National University of Ireland in 2010 as well as an award from the Alexander von Humboldt Foundation, Germany in 2011. He has been awarded the 2020 Tom W. Bonner Prize of the APS.