Maize ( /ˈmeɪz/ MAYZ; Zea mays L, from Spanish: maíz after Taíno mahiz), known in some English-speaking countries as corn, is a grain domesticated by indigenous peoples in Mesoamerica in prehistoric times. The leafy stalk produces ears which contain seeds called kernels. Though technically a grain, maize kernels are used in cooking as a starch. The Olmec and Mayans cultivated it in numerous varieties throughout Mesoamerica, cooked, ground or processed through nixtamalization. Beginning about 2500 BC, the crop spread through much of the Americas. The region developed a trade network based on surplus and varieties of maize crops. After European contact with the Americas in the late 15th and early 16th centuries, explorers and traders carried maize back to Europe and introduced it to other countries. Maize spread to the rest of the world because of its ability to grow in diverse climates. Sugar-rich varieties called sweet corn are usually grown for human consumption, while field corn varieties are used for animal feed and as chemical feedstocks.
Maize is the most widely grown grain crop in the Americas, with 332 million metric tons grown annually in the United States alone. Approximately 40% of the crop — 130 million tons — is used for corn ethanol. Transgenic maize (genetically modified corn) made up 85% of the maize planted in the United States in 2009. While some natural strains of maize can grow 12 metres (39 ft) tall, most varieties commercially grown for grain have been bred for a standardized height of 2.5 metres (8.2 ft). Sweet corn is usually shorter than grain and silage corn varieties.