Ecosystems first came to the attention of managers and management scholars in the 1990s and early 2000s. Beginning with the IBM PC in 1981, the success and rapid pace of innovation in the computer industry showcased the power of modular technical systems in combination with managed business ecosystems. However, ecosystems are not a one-size-fits-all solution that can be easily designed and set up by any group of firms. On the contrary, sustainable ecosystems are the result of a delicate balance between, on the one hand, forces that push economic activities toward integration into a single corporation and, on the other hand, forces that pull economic activities out onto the market. We call these forces centripetal and centrifugal forces, respectively. Ecosystems evolve when these forces change. For example, technological complementarities—the main source of centripetal force—are dynamic and may be commoditized, generalized, or standardized over time. Management and coordination also change: for example, open innovation practices enable firms to move innovation activities from the in-house R&D lab out into the ecosystem. This article discusses how such dynamics in technologies and management lead to ecosystem evolution.