A crop is a plant or plant product harvested for human use. Crops are cultivated at scale to produce food, fiber, fuel, and other products. Crops have been central to human civilization since the first agricultural revolution, a key stage in the broader history of agriculture, when early societies domesticated plants for food and trade. Today, a small number of staple crops such as rice, wheat, maize, and sugarcane account for the majority of global production. Because of their economic importance, crops are studied within several scientific disciplines, including agronomy, agricultural science, horticulture, and forestry.