This volume presents an overview of Jean Piaget's work in psychology - from his earliest writings to posthumous publications. It also contains a glossary of the essential explanatory concepts found in this work. The focus is on Piaget's psychological studies and on the underlying epistemological theses. The book may be consulted in various ways depending on whether one is looking for an introduction to Piaget's theory, details about a particular concept, a survey of his body of work, or an historical perspective. Readers who are relatively unfamiliar with Piaget's ideas and seek access to them through this book will not necessarily proceed in the same way as those who are acquainted with Piaget's work and wish to refresh, synthesize or complete their knowledge. The volume is divided into two major sections with several subdivisions as follows: the chronological overview presents Piaget's early ideas and the most important source of his inspiration, and reviews his research work dividing it into four main periods plus a transitional one; and the glossary covers a number of explanatory concepts which are essential to Piaget's theory.