The problem that gestalt theory confronts is that of an extended event, whether an experience or an action, that cannot be adequately described as a sum of smaller, independent events. Such an event is called a gestalt; this term can be translated as “form,” “configuration,” or “structure.” Facts of this character were largely ignored in the atomistic psychology of the nineteenth and early twentieth centuries, although a few thinkers had begun to question this neglect. The gestalt movement introduced a new approach to the treatment of psychological facts. It arose in Germany in the second decade of the twentieth century as a reaction against atomistic psychology. Its founders and pioneers were Max Wertheimer, Wolfgang Köhler, and Kurt Koffka. The first 25 years of its existence were a period of rapid development of ideas and of intensive investigation. Beginning with the 1920s it commanded wide attention in the psychological world. With the rise of Nazism the leading gestalt psychologists left Germany for the United States, and the subsequent course of the movement became, in a measure, part of the history of American psychology. [See the biographies ofKoffka; KÖhler; Wertheimer.]