This paper explores the roots of dynamic organizational capabilities. We suggest that streams of innovation are central to a firm's ability to compete over time. We argue that organizational design is an important determinant of innovation streams and that these streams can be effectively executed within organizations through ambidextrous organizational designs. Based on in-depth data on 15 business units and 36 innovation episodes we explore the consequences of organizational design choices on innovation outcomes. We explore the phenomena of ambidextrous organizational designs -- what they are, how they operate, and their association with innovative outcomes. We also explore their boundary conditions as well as how these complex organizational forms evolve.