The recognition that aging processes are considerably influenced by the individuals' life-course from birth on can be traced to antiquity. One of the first attempts of scientific study of the entire life-course was started by Charlotte Bühler (1933). Already in 1951, Thomae emphasized the necessary extension of Developmental Psychology from its restriction to childhood into covering the entire life-span, and initiated numerous empirical studies working with the biographical method. Thus, the "life-span-orientation" of Developmental Psychology, recently ascribed to P.B. Baltes, is rather a rediscovered conceptualization than a genuine 'new' idea. Following this evaluation of the historical roots and origins of "life-span-developmental-psychology", a review of empirical biographical studies is presented, which emphasize a conceptualization of behavior in older age at the intersection of past experience, current situation, and future time perspective of the individual. As an example it is discussed how the mother experiences and reacts to her (last) child's leaving home ("empty-nest-reaction"). In addition, "sociogendtic risk-factors" (Eitner) are discussed, as well as the biographical interdependency of mental and physical activity, of multiple interests and social contacts. Stating the empirical evidence for the strong influence of behavior and experience in younger and middle adulthood on the individual's well-being in older age must not lead to the conclusion that the situation of the aged person cannot be changed: the older individual certainly has the ability and opportunity to learn, to be flexible, and to change--within the given boundaries--his current situation.