Bran, the outer layers of cereal grains (such as wheat and oats). Bran is a good source of carbohydrates, calcium, phosphorus, and fiber.
In the manufacture of white flour from wheat, the bran is removed. In whole-wheat flour, the entire kernel of wheat, including the bran, is ground to flour; in graham flour, only part of the bran is removed. Most of the bran removed from wheat is used to provide bulk and protein in animal feeds. Wheat and oat brans are used in breakfast cereals and in bakery goods because of their dietary-fiber and relatively high protein content.
also Oats, picture titled Inside an Oat Grain; Wheat, picture titled Inside a Kernel of Wheat.