This chapter introduces the theory of practice architectures and locates it within the theoretical terrain of practice theory. It highlights what is distinctive about the theory as a practice theory, and discusses its affordances as a theoretical, analytical, and transformational resource for practitioners and researchers. We argue that, to create new possibilities for practice in our disciplines and professions, and/or to challenge unsustainable or untoward practices in education and professional practice more broadly, our current practices must be interrogated. The theory of practice architectures can inform such interrogative work. This chapter provides a foundation for the case chapters in this book which variously illustrate the kinds of insights yielded by exploring education and professional practice through the lens of practice architectures.