In Huangdi Neijing, the five grains are considered as "japonica rice, adzuki bean, wheat, soybean and millet", while in Mencius Teng Wen Gong, they are called "rice, millet, millet, wheat and rice", and in Buddhist sacrifices, they are also called "barley, wheat, rice, adzuki bean and flax". At present, the general term "whole grains" refers to rice, wheat, sorghum, soybeans and corn, while the grains other than rice and flour are customarily referred to as whole grains, so whole grains also refer to food crops.

Grains: the general term for food crops. The theory of "five grains" appeared in the Spring and Autumn Period and the Warring States Period. The Analects of Confucius: "Four bodies are not diligent, and five grains are not divided." But the explanations are different, one is millet, millet, wheat, rice; When it comes to millet, millet, wheat, millet and hemp. The main difference between these two statements lies in the existence of rice and hemp. The reason for the disagreement is that there were more than five kinds of crops at that time, and the existence of the theories of "100-grain", "6-grain" and "9-grain" is a clear proof, and the varieties of crops in different places are different. The popularity of the theory of "five grains" is obviously caused by the influence of the five elements. Therefore, generally speaking, grains refer to several major food crops.

Although the concept of five grains has been in existence for more than two thousand years, the status of these crops in the national food supply has changed from time to time. Millet, millet and other crops in the five grains have the characteristics of drought tolerance, barren tolerance and short growth period, so they occupy a particularly important position in the original cultivation of dry land in the north. By the Spring and Autumn Period and the Warring States Period, the characteristics of "keeping old and being easy to do" were discovered, and it became an indispensable food for people at that time together with millet. At the same time, it has been found that lodging wheat (winter wheat) can be planted in late autumn and early spring, and it can solve the problem of green and yellow. In addition, the invention of stone mill at this time has greatly improved the palatability of wheat from grain to pasta, which has attracted widespread attention and developed into one of the main food crops, and is comparable to millet. In the Confucian classic "Spring and Autumn Annals", it is not a book, but it is a book if the grain and wheat fail. It can be seen that saints attach the most importance to wheat and grain among the five grains. Agronomists Zhao Guo and Fan Sheng Zhi in the Western Han Dynasty devoted themselves to popularizing wheat planting in Guanzhong area. The increase of Guanzhong population in Han Dynasty was closely related to the development of wheat farming. Until the Tang and Song Dynasties, the population in the north was more than that in the south. But after the Tang and Song Dynasties, the situation changed. China's population growth is mainly concentrated in the southeast, which has been called "a vast territory with a vast population" since the Qin and Han Dynasties. Hey? Street? Hey, k? Play dumplings and silk? A sword? Fissland profile? ：4； Since then, the population density in the south has been much higher than that in the north. The increase of population in South China is inseparable from rice production. Rice is very suitable for planting in the southern region with abundant rainfall, but at first it was inconspicuous and even excluded from the grain. However, it came from behind. After the Tang and Song Dynasties, the status of rice in the national food supply was increasing day by day. According to Song Yingxing's estimation in the Ming Dynasty, at that time, seven tenths of rice was dominant in the food supply, while rice, wheat, millet, millet and other food crops, together, accounted for only three tenths of the total, which had been relegated to a secondary position. Soybean and hemp had withdrawn from the category of food crops and were only used as vegetables. However, when some crops withdrew from the ranks of grain crops, some crops joined the ranks of grain crops. At the end of the Ming Dynasty, corn, sweet potato and potato were introduced to China one after another and became an important part of the main grain crops in modern China.