The pace at which the concept and language of collective impact have spread over the last three years is inspiring. We are encouraged to see that many organizations in the social and private sectors have embraced the concept as a new way to achieve large-scale systems change. Practitioners, funders, and policymakers have begun to recognize that solving complex social problems at a large scale can happen more effectively when actors work together, rather than through isolated programs and interventions—a tremendously important shift for the field