Book excerpt: In Economics, networks are increasingly used to describe the many links created between independent companies, as well as between them and other institutions (universities, banks, venture capital, etc.). In the current global and knowledge-based economy, they can be characterised as knowledge factories and knowledge boosters. They feed the internal processes of innovation (collaborative innovation) or the external processes of innovation, created by the propagation effects that come from inter-firm collaboration. The book explains how innovation networks are at the origin of the production of new knowledge that will be transformed and used in common as well as in separated production processes. This characteristic of networks as knowledge factories gives incentives to further investment in the production of knowledge and ensures the cumulativeness of the innovation process. Some of the authors clearly take a territorial point of view and study how clusters (in different parts of the world: Europe, Eastern Asia and North America) propelled by the quality of the innovation networks they enclose, can be characterised as knowledge pools into which the local actors will be able to draw to reinforce their individual and collective competitiveness. This book also includes analyses of the quality of the networks built within clusters, which may help their identification.