During the 1980s the Marshallian concept of industrial district (ID) became widely popular due to the resurgence of interest in the reasons that make the agglomeration of specialised industries a territorial phenomenon worth being analyzed. The analysis of clusters and IDs has often been limited, considering only the local dimension of the created business networks. The external links of these systems have been systematically under-evaluated. This book offers a deep insight into the evolution of these systems and the internal-external mechanism of knowledge circulation and learning. This means that the access to external knowledge (information or R&D cooperative research) or to productive networks (global supply chains) is studied in order to describe how external knowledge is absorbed and how local clusters or districts become global systems. It provides a unified approach; showing that existing capabilities expand when locally embedded knowledge is combined with accessible external knowledge. In this view, external knowledge linkages reduce the danger of cognitive 'lock-in' and 'over-embeddedness', which may become important obstacles to local learning and innovation when technological trajectories and global economic conditions change. It features a selection of international experts.