The field of chronic disease is primarily concerned with the role of early life exposures and early life conditions in adult disease. Specifically, the fetal origins of adult disease (FOAD) hypothesis suggests that exposures, events, or insults that occur in early development, specifically during pregnancy, may have an effect on risk of adult disease in offspring. This entry briefly explores the history leading up to this hypothesis, discusses developments, and highlights the current state of the field. This entry also discusses the significance of this approach over earlier approaches to adult disease as well as future directions.