War and terror, demographic imbalances, unchecked climate change, and rampant criminality are the drivers of catastrophic migrations. In the first quarter of the twenty-first century, we witnessed the largest number of forcefully displaced human beings in record. Concurrently the world is now facing the largest “crisis of confinement” in history, leaving millions of human beings in search of shelter far away from the high and middle-income countries, lingering in interminable limbo. In the aftermath of World War II, Europe, the United States, and their allies developed policies for forcefully displaced refugees based on the assumption that whatever caused them to flee their homes would be resolved and refugees would return home. These architectures, we argue, are misaligned with the new conditions. Devastated environments in states with weak institutional capacities hold little promise for safe return. A new twenty-first-century cartography of mass migration suggests forms of migration that do not fit existing policy frameworks. First, most forcefully displaced migrants today stay as internally displaced either in their own countries or in camps in neighboring states often in subhuman conditions with few protections. Second, protracted conflicts are sending millions fleeing with no expectation of returning. Third the architectures in place are generally blind to the developmental needs of children. Crying children are the face of the catastrophic migrations of the twenty-first century. Worldwide, one in every two hundred children is a refugee, almost twice the number of a decade ago. In 2017, there were over twenty-eight million children forcefully displaced. For the first time in history, over half of all refugees under the United Nations High Commissioner for Refugees mandate are minors. Even when temporary protection is possible or desirable, children in flight need more than a safe haven. They need a place to grow up. They need the safety of home. In this Introduction we review the best evidence and current thinking on physical health, mental health, and trauma; legal protections; and education for forcefully displaced children and youth.