Wheat and rye are cereal plants, which are grasses. These grasses produce seeds that are an excellent food source for humans and animals. The grains have edible inner portions called the endosperm, germ and bran. Typically, only the endosperm is used in processed foods. Wheat germ contains vitamins and fiber, and is often used to boost the nutritional content of foods. The bran is the outer layer of the grain and contains fiber and some fatty acids.