The document discusses clusters and innovation ecosystems. It defines clusters as concentrations of interconnected companies, suppliers, and associated institutions in a particular field that reach a critical mass. It also describes innovation ecosystems as networks of actors that exchange knowledge and people within a regional context. The document provides examples of successful clusters like Silicon Valley. It identifies factors for successful clusters, such as talent flow, specialized knowledge, and policy support. It also notes areas where Europe lags clusters in the US, such as tenure length, national science competition, and an innovation arena dominated by large players. The document concludes that knowledge is an underutilized resource in innovation ecosystems and that people are the most important factor for cluster success.