Rolf Loeber and Magda Stouthamer-Loeber were born in the Netherlands in 1942, met at Leiden University in 1967, and, from then on, worked and lived together until Rolf’s death half a century later. Their first faculty appointment was at the University of Pittsburgh in the United States, after having published seminal papers on the stability of antisocial behavior and the first meta-analysis of predictors of delinquency. The Loebers had major impacts on the science of violent behavior development and on the translation of this scientific knowledge into improved public policy. They pioneered the articulation and expansion of developmental and life-course criminology. They clarified the formulation of key concepts, and initiated as well as maintained two landmark longitudinal studies which started in childhood and continued with regular assessments into early adulthood: The Pittsburgh Youth Study (PYS) and The Pittsburgh Girls Study. The latter was the first major large-scale study in the United States on the development of female delinquency between childhood and early adulthood. The Loebers were the first to have the data to study youths who are at highest risk to commit homicide or become victims of homicide. They showed that the processes leading to homicide were often in place during late childhood.