In a time where governments and civil society organizations are putting ever-greater stock in social innovation as a route to transformation, understanding what characterizes social innovation with transformative potential is important. Exciting and promising ideas seem to die out as often as they take flight, and market mechanisms, which go a long way towards contributing to successful technical innovations, play an insignificant role in social innovations. The cases in this book explore the evolution of successful social innovation through time, from the ideas which catalysed social and system entrepreneurs to create new processes, platforms, projects and programmes to fundamental social shifts in culture, economics, laws and policies which occurred as a result. In doing so, the authors shed light on how to recognize transformative potential in the early stage innovations we see today. This comparison of multiple historical cases across problem domains creates a map of social innovation over time - shifting our thinking on both current issues and established programmes. From the American National Parks and the Joint Stock Company to the intelligence test and the financial derivatives that led to the 2008 crash, this book acts as a useful reflection and a cautionary tale, looking back to gain insight and inform the vibrant discussion of social innovation's future. This book pushes theoretical and methodological boundaries of the field through approachable narratives, making it an ideal resource for social innovation students, scholars, instructors and practitioners.