The common bean, Phaseolus vulgaris, is an herbaceous annual plant domesticated independently in ancient Mesoamerica and the Andes, and now grown worldwide for its edible bean, popular both dry and as a green bean. The leaf is occasionally used as a leaf vegetable, and the straw is used for fodder. Botanically, the common bean is classified as a dicotyledon. Beans, squash and maize constituted the “Three Sisters” that provided the foundation of Native American agriculture. Beans are a legume and thus acquire their nitrogen through an association with rhizobia, a species of nitrogen-fixing bacteria. 18.3 million tonnes of dry common beans and 6.6 million tonnes of green beans were grown worldwide in 2007. The other major type of beans is broad beans, of which only 3.7 million tonnes were grown in 2007. The commercial production of beans is well-distributed worldwide with countries in Asia, Africa, Europe, Oceania, South and North America all among the top bean growers. Brazil and India are the largest producers of dry beans while China produces, by far, the largest amount of green beans, almost as much as the rest of the top ten growers altogether.