Masa is a dough made from nixtamalized corn: dried field corn that has been cooked and soaked in an alkaline, usually lime, solution and then ground while wet. Nixtamalization loosens the corn's hull and increases the availability of niacin and other nutrients. Masa is the base for corn tortillas, tamales, and pupusas, and its dried, powdered form is sold as masa harina, a shelf-stable product used to make fresh masa at home.