While intense efforts of clarification have been made to distinguish between the concept of system and ecosystem, and between the different forms of ecosystems, very few works have addressed the issues of how these different forms of ecosystems are interacting in a dynamic perspective, or of how the notion of a dynamic ecosystem could emerge from the static frame of a system approach. The five chapters in this volume precisely aim at adding to this literature by highlighting the interplay between different types of innovation systems. A common thread among the five chapters of the book is the recognition of the need to develop new lenses to formally account for adaptative behaviour within clusters, networks, or regional innovation systems using the ecosystem metaphor. The diversity and heterogeneity of agents, the complexity of relationships, and new forms of organisation (underground, middleground, and upperground) are the main characteristics of innovation ecosystems, in contrast to more traditional concepts like clusters or networks. In essence, the five chapters add various complexity dimensions (relationships, knowledge, systems, etc.) to the existing knowledge on ecosystems. The chapters in this book were originally published as a special issue of the journal Industry and Innovation.