Breakfast cereal (or just cereal) is a food made from processed grains that is often eaten as the first meal of the day. It is eaten hot or cold, usually mixed with milk, yogurt, or fruit.Some companies promote their products for the health benefits from eating oat-based and high-fiber cereals.n 1902 Force wheat flakes became the first ready-to-eat breakfast cereal introduced into the United Kingdom. The cereal, and the Sunny Jim character, achieved wide success in Britain, at its peak in 1930 selling 12.5 million packages in one year. In the 1930s, the first puffed cereal, Kix, went on the market.