Wheat is a grain which is used to make wheat flour, a common ingredient in many types of food, such as bread, cakes, cookies, and pasta. Depending on which parts of the grain are included in the flour, there are different varieties of wheat flour with different nutritional values and baking qualities. For example, white flour is used for softer pastries, while whole wheat flour is used for dense and nutritious varieties of bread. Flour is stored in large silos, and though very space-efficient, it does require extra work in the form of grinding, normally done by simple machinery these days. Setting fires close to places where flour is stored is very dangerous since, like all powders, it can set off a catastrophic explosion.