Sustainability science has developed from a new research field into a vibrant discipline in its own right, with scientific conferences, journals and scientific societies dedicated to its pursuit. Characterized more by its research purpose than by a common set of methods or objects, sustainability science can be subdivided into the more traditional disciplinary-based science for sustainability and the transdisciplinary science of sustainability. Whereas the former consists of more descriptive, analytical and basic science, the latter is characterized by reflexivity and applicability; on a meta level, the emergence of the latter can be understood as a new step in the evolution of science. This review provides an overview of the state of sustainability science, identifying action orientation, integrated assessments and interdisciplinarity as overall characteristics. The review also focuses on methodological issues, highlighting differences in project organization and management, and the ways in which stakeholder participation can be organized in interdisciplinary and transdisciplinary research projects. Sustainability science is recognized as essential for progress towards sustainability, and as an opportunity to bring science closer to the people, requiring significant changes in the way science is organized and conducted.