Developmental psychologist Paul B. Baltes (1939-2006) was born in Saarlouis, Germany. After studying in Germany he moved to the United States, where he continued the conceptual and methodological quest of his doctoral dissertation to transform developmental psychology into a science that seeks to describe, explain, and modify individual differences in behavioral development across the entire life span. His work was pivotal in establishing life span psychology as a comprehensive and distinct theoretical orientation within contemporary developmental psychology. Paul Baltes' career was characterized by internationality, interdisciplinarity, generativity, societal concern, and institutional prudence and sagacity. One of his central research interests was to explore age-graded changes in the range of plasticity in individual development, with the goal to identify and promote personal and societal conditions that favor successful aging. At the same time, he was not negligent of the negative sides of very old age, and spoke of old age and aging as 'hope with a mourning band.'.