A cereal is any edible components of the grain (botanically, a type of fruit called a caryopsis ) of cultivated grass , composed of the endosperm , germ , and bran . Cereal grains are grown in greater quantities and provide more food energy worldwide than any other type of crop [1] and are therefore staple crops . Edible grains from other plant families, such as buckwheat ( Polygonaceae ), quinoa ( Amaranthaceae ) and chia ( Lamiaceae ), are referred to as pseudocereals . In their natural form (as in whole grain ), cereals are a rich source of vitamins , minerals , carbohydrates , fats , oils, and protein . When refined by the removal of the bran and germ, the remaining endosperm is mostly carbohydrate . In some developing countries , grain in the form of rice , wheat , millet , or maize constitutes a majority of daily sustenance. In developed countries , cereal consumption is moderate and varied but still substantial. The word cereal is der