Klein is Carnell Professor of Science and Dean of Science and Technology, at Temple University, Philadelphia, USA. He was Hepburn professor of physical science and director, Lab. for Research on the Structure of Matter, Univ. of Pennsylvania (UPenn), Philadelphia. After his PhD (Univ. of Bristol) and postdoctoral work in Italy, England, and USA, he joined the National Research Council of Canada. In 1987, he joined UPenn where he established the Center for Molecular Modeling. He is member of the National Academy of Sciences of the USA, a fellow of: Royal Society of London; Royal Society of Canada; and American Academy of Arts and Sciences. Awards include: American Physical Society Aneesur Rahman Prize for Computational Physics; American Chemical Society Debye Award in Physical Chemistry; and Bernie J. Alder CECAM Prize, European Physical Society.