Edith Penrose has been one of the most significant economists of the second part of the twentieth century. Her contribution to the theory of the firm has reinvented and productively developed the classical tradition in economics, and informed the currently dominant, knowledge-based theory of the firm. This volume builds on a special issue of Contributions to Political Economy that celebrated forty years since Penrose's classic The Theory of the Growth of the Firm. It includes fifteen chapters by leading contributors on the aforementioned aspects of Penrose's work.