This book calls for the conditions of transition to sustainability: How to take into consideration new global phenomena such as and of the dimension of climate change, the depletion of natural resources, financial crises, demographic dynamics, global urbanization, migrations and mobility, while bearing in mind short-term or local place-based issues, such as social justice or quality of life? Meeting this challenge requires an inclusive approach of sustainability. It is a matter of designing a new social contract: Sustainability requires more than developing the right markets, institutions and metrics, it requires social momentum. To do so, many issues need a clear and complete answer: How to link social justice with sustainability policies? What governance tools to do so? What linkage between one decision-making level and the other? These are major issues to design sound transitions to sustainability.