Flour is a powder made by grinding uncooked cereal grains or other seeds or roots (like cassava). It is the main ingredient of bread, which is a staple food for many cultures, making the availability of adequate supplies of flour a major economic and political issue at various times throughout history. Wheat flour is one of the most important ingredients in Oceanic, European, South American, North American, Middle Eastern, Indian and North African cultures, and is the defining ingredient in their styles of breads and pastries.