In March 1991 the ESF Network on Longitudinal Studies on Individual Development completed its five-year existence with a summing-up conference in Budapest, Hungary.

The conference was built round poster sessions which were interspersed with state-of-the-art lectures by prominent scholars in various important areas. In order to make the present volume, which in the main emanates from this conference, cover the various research domains as adequately as possible, some additional scholars were invited to write chapters with respect to some of the more comprehensive fields.

In this introduction, we will try to summarize some pivotal issues in each of the chapters and also make attempts at highlighting the holistic and dynamic facets of human development. This is one important and recurrent theme in all chapters, although naturally formulated in different ways by the various contributors.

In Chapter 1, Magnusson presents a number of arguments in favour of more concentrated efforts being devoted to longitudinal research for the study of the intricate processes that mould individuals' future lives. He emphasizes the importance of rendering research on human ontogeny more vigorous by complementing the more traditional variable-oriented approaches with studies that focus on persons as the central unit of analysis. Magnusson purports that humans can be seen from a general systems theory, and also that each individual is a self-organizing system. The latter concept implies that subsystems, physiological and psychological, interact and organize in ways to optimize the functioning of the whole organism. Incidentally, the word ‘organ’ means ‘tool’ in Greek and ‘organism’ refers to an ‘ordered structure’ of interacting mechanisms.