Consumers, producers, critics, and other market agents rely on socially constructed categories like “craft” beers, houseware “collectibles”, and “thriller” films for their understanding of products and producers in markets. Although organizational and sociological accounts often take such categories as given, researchers increasingly acknowledge that category emergence, development, and functioning represent key aspects of how markets work. Take, for example, the U.S. brewing industry, which has become segmented into mass versus specialty producers. Many beer lovers who appreciate the characteristics of a beer made by small, specialty breweries are not willing to buy an equivalent beer made by an integrated, major producer. Knowledge of what specialty beer has come to mean and represent to consumers as the product of an authentic, artisanal production process and delivery is crucial for our understanding of how this market and competitive dynamics within it have evolved. This volume focuses on how market categories shape processes of production and consumption and how these activities in turn shape category systems. This volume consists of original contributions to theory and empirical research by a diverse group of esteemed authors. Topics explored include how new categories emerge, become enacted and gain consensus, how categories are used by market agents (including as tools for interpretation, as mobilization frames, and as cognitive infrastructures for learning), and how category systems change over time. These topics are explored from a variety of perspectives: new institutional theory, organizational ecology, social movement theory, and socio-cognitive theories of markets. The breadth of perspectives in this volume attests to the importance of this topic to sociological studies of market processes.