For a long time, research on developmental issues in the biological and social sciences was mostly concerned with the early parts of life, such as infancy and adolescence. Studies paying full attention to people after they had passed through late adolescence were rare even though we all know that humans continue to develop. The dynamics of adult life can be as forceful and full of transitory states as is life before 20. Individual development is a lifelong process: from the moment of conception to the moment of death. Recently, more and more researchers have turned their attention to the problems of development and aging in later periods of life. This increased interest is caused partly by growing social demands from the aged generations in many Western countries and partly by the fact that longitudinal research endeavors have now started to yield impressive results concerning life-span development.

Developmental problems cannot be very well investigated and understood in all their facets without a solid longitudinal methodology. Therefore, the European Network on Longitudinal Studies on Individual Development (ENLS), established by the European Science Foundation, decided to devote special attention to the issues of aging. One tangible indication of the network's commitment to this area of research is the volume you are now holding in your hands. This volume contains a number of contributions from prominent European and American scientists actively involved in research on aging, providing us with stimulating insights into and a new understanding of the multifaceted and highly complex process of life-span development.