This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book shows how ethnic and religious differences can be mitigated, how relationships with surrounding host states can be negotiated, and how political representation and democratic choices can be maximized. It describes how the economy and security of each refugium can be optimized. The book provides a discussion about the potential and limitations of block chain technology to animate some of the objectives of Refugia. Mass displacement is one of the most pressing global issues of our time. Many more people are being driven from their homes: more than 70 million people worldwide were forcibly displaced by the end of 2018, including nearly 26 million refugees, 41 million internally displaced people, and 3.5 million asylum seekers.