For decades, researchers in customer management have demonstrated the business importance of firm-customer relationships, developed models for understanding customer behavior and response to marketing, established the link between customer behavior and firm performance, and proposed policies to optimize customer management activities. This paper overviews customer management research, from its historical origins to its recent developments. We identify promising directions for future research, with an emphasis on novel data sources, online marketplaces, and new technologies; additionally, we highlight the privacy and fairness considerations that come with these developments.