This book studies “communities of knowledge,” a concept that goes beyond the notion of communities of practice to analyze the structure of the emergent knowledge societies. A complex society has to be integrated by various and heterogeneous communities and a knowledge society should be based on the plurality of communities of knowledge. This was the main hypothesis behind the organization of the “International Conference on Knowledge Communities,” which is at the origins of this book. A selection of updated versions of the papers presented at the conference is found in this volume. Our intention was to examine the structure of knowledge-based societies, while exploring new modalities of innovation, in addition to those based on science (e.g., e-science) and engineering. The chapters of this book are an in-depth examination of the concept of knowledge communities and address scientific, engineering, and artistic communities as well as online communities with particular interest on the development of knowledge societies.