Although knowledge flows are a popular concept, the underlying dynamics are not well understood. This article develops a perspective that conceptualises the social and cognitive activities that make knowledge flows possible. Dynamics involve interactions between local and global levels, and dedicated aggregation activities by intermediary actors. An idealtypical four-phased pattern is developed to understand the creation of global knowledge. The socio-cognitive perspective is illustrated with a historical case study, the emergence of reinforced concrete (1850-1940). The concluding section formulates policy implications for nurturing the emergence of radically new technologies. © Beech Tree Publishing 2006.