Research and development are at the core of CCT's work. We draw on a range of methodological approaches in our research in response to the needs of particular projects. Although we work with many different partners on a wide range of topics, two core principles are shared across our R&D projects. First, our work gives the highest priority to the needs and perspectives of teachers and students and the particular, complex contexts they work in. Second, we take a design-based perspective on the relationship between research and development, using an iterative, exploratory process to help us craft resources that model powerful, innovative approaches to improving teaching and learning.