Formative and design experiments represent a methodology uniquely suited for educational research. Providing a practical overview of this emerging approach, the authors address the following questions: What is the origin of formative and design experiments and how do they compare to other approaches to investigating interventions in classrooms? How do you conceptualize, plan, conduct, and report formative and design experiments? What practical, ethical, and methodological issues might be encountered? What is the future potential of this promising approach?