Understanding money's nature as political, institutional, and material answers today's big money questions. Money remains a foundational question of social theory. What is money? Why does something so insubstantial have value? How do money systems make promises function like valuable things? Why are money systems always hierarchical yet variable? The answer, the book argues, is politics. Money is institutionalised social power. Politics generates institutions that differentially lock into the future product of political and economic collectives. Money emerges from the institutionalisation of social antagonisms to encapsulate a collective's productive potential in a flexible, tradable instrument. This takes a system. Money is built in hierarchical layers out of the inherently variable material of politics and at various economic scales. This book outlines these variable processes theoretically and through case studies.