Mexicans identify themselves as the “people of maize”. The cultural area of Mesoamerica is a primary heart of crop domestication and agricultural evolution in the world. The traditional “milpa” field is intercropped with three principal species, maize, beans and squash. Farmers also tolerate and harvest useful weeds. Their homegardens, “solares”, are places of enjoyment and experimentation, and an important source of goods. Through hundreds of generations Mesoamerican farmers have selected and exchanged seeds, and improved or created new landraces. The milpa-solar system ensures a high production of rich, balanced and diverse food crops from small areas. Its protection, and also reintroduction, is of great importance, in particular as it is the world's reservoir of maize genes.