Corn is millet. Corn is one of the earliest domesticated cultivated grains in China, with a history dating back to the middle of the Neolithic period. Corn is drought-resistant and barren, and is the main food crop in the northern region, where it is known as "grain", and in the southern region as "millet". Corn varieties, white, red, yellow, black, orange, purple and other colors. After the Middle Tang Dynasty, rice gradually replaced corn in the food crops in the primary position, and thereafter, the status of wheat also gradually exceeded corn. Thus, China's agricultural grain crop structure from corn, wheat-based, evolved to rice, wheat-based.