This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book describes how crisis and migration articulate, as lived experiences and as political constructs, by examining a range of situations around the world. It explores ways of conceptualising crisis and migration, sketching out key issues and inter-linkages. The book examines the mobility environment broadly speaking, including well-recognised and emphasised migration patterns, but also offering insights into immobility, people's diverse micro-negotiations of space and routine, and politically less visible migration patterns. It shows how Sudanese refugees both experience and manage crisis through the family, transforming and adapting family relations in protracted displacement, even dispersing further in pursuit of individual and collective goals. The book shows how migration is central to how people experience and respond to crisis showing how individuals, families and communities use mobility in sometimes pre-emptive, often reactive, and other times more strategic fashion.