Grains are small, hard, dry seeds, with or without attached hulls or fruit layers, harvested for human or animal consumption. The two main types of commercial grain crops are cereals (e.g. wheat, rye) and legumes (e.g. beans, soybeans). Seeds
After being harvested, dry grains are more durable than other staple foods, such as starchy fruits (e.g. plantains, breadfruit) and tubers (e.g. sweet potatoes, cassava). This durability has made grains well suited to industrial agriculture, since they can be mechanically harvested, transported, stored for long periods, and milled for flour or pressed for oil. Major global commodity markets exist for canola, maize, rice, soybeans, wheat, and other grains but not for tubers, vegetables, or other crops.