Efforts to design, use, and do research on educational tools and materials in real settings can promote the adoption of innovations. They can help researchers and designers understand the real-world demands placed on designs and on adopters of designs. In addition, pursuing development and enactment through close collaboration with teachers places them in direct ownership of designs. Although design-based research is positioned to address these issues, sustaining innovations hinges on our ability to articulate the mechanisms that underlie their success.