This book was written to help people understand and transform education and professional practice. It presents and extends the theory of practice architectures, and offers a contemporary account of what practices are composed of and how practices shape and are shaped by the arrangements with which they are enmeshed in sites of practice. Through its empirically-based case chapters, the book demonstrates how the theory of practice architectures can be used as a theoretical, analytical, and transformational resource to generate insights that have important implications for practice, theory, policy, and research in education and professional practice. These insights relate to how practices are shaped by arrangements (and other practices) present in specific sites of practice, including early childhood educationsettings, schools, adult education, and workplaces. They also relate to how practices create distinctive intersubjective spaces, so that people encounter one another in particular ways (a) in particular semantic spaces, (b) that are realised in particular locations and durations in physical space-time, and (c) in particular social spaces. By applying such insights, readers can work towards changing practices by transforming the practice architectures that make them possible.