Flour is a powder made by grinding raw grains, roots, beans, nuts, seeds, or bones. Flours are used to make many different foods. Cereal flour is the main ingredient of bread, which is a staple food for most cultures. Wheat flour is one of the most important ingredients in Oceanic, European, South American, North American, Middle Eastern, North Indian, and North African cultures, and is the defining ingredient in their styles of bread and pastries. Corn flour has been important in Mesoamerican cuisine since ancient times and remains a staple in the Americas. Rye flour is a constituent of bread in central Europe.