Jeffrey is a graduate of MIT (SB, SM) and of the University of Chicago (PhD). In Chicago, he worked at Fermilab and at Argonne National Lab. He moved to Aarhus University in Denmark in 1993 and has been there since. He received the European Physical Society’s 1996 accelerator award for a young scientist for his work on laser cooling of stored ion beams in the ASTRID storage ring in Aarhus. He is a founder of the ATHENA antihydrogen collaboration and was the Physics Coordinator of the experiment that produced the first cold antihydrogen atoms at the CERN Antiproton Decelerator in 2002. He is founder and spokesperson of the ALPHA collaboration at CERN, which demonstrated trapping of antihydrogen atoms in 2010, and the first laser spectroscopy of antihydrogen in 2016. He holds numerous prestigious awards and is a member of the Royal Danish Academy of Sciences and Letters.