The hidden curriculum (HC) is a theoretical construct that refers to the unofficial rules, routines, and structures (both social and physical) of environments through which all participants (e.g., students, employees, leaders, etc.) come to learn the behaviors, values, beliefs, and attitudes expected of them. This entry provides a brief tour through the history of the concept in the two fields (sociology and education) where it has garnered the most attention. Using medicine and medical education as an example, it explores several recent developments, such as a shift from systems toward individuals, as well as current efforts that draw from a variety of fields (such as complexity science) to intervene upon learning environments. It concludes with a suggestion for future sociological work on the construct.