Soybean is widely planted in China, from northeast to north China, from Shaanxi and Sichuan to the middle and lower reaches of the Yangtze River. Soybean was introduced to the United States in the19th century, and by the middle of the 20th century, soybean had become an important agricultural product supporting the central and western regions. Soybean is favored all over the world because of its high nutritional value. The ancients called it "meat in the field" and "green milk".