The origins of the soybean plant are obscure, but many botanists believe it was first domesticated in central China as early as 7000 bce. An ancient crop, the soybean has been used in China, Japan, and Korea for thousands of years as a food and a component of medicines. Soybeans were introduced into the United States in 1804 and became particularly important in the South and Midwest in the mid-20th century. Brazil and Argentina are also major producers.

The soybean is an erect branching plant and can reach more than 2 metres (6.5 feet) in height. The self-fertilizing flowers are white or a shade of purple. Seeds can be yellow, green, brown, black, or bicoloured, though most commercial varieties have brown or tan seeds, with one to four seeds per pod.