The first modern and commercial cereal foods were created by the American Seventh-day Adventists. The Adventists formed the Western Health Reform Institute in the 1860s. The Institute was later renamed the Battle Creek Sanitarium after its location in Battle Creek, Michigan. The Adventists manufactured, promoted, and sold wholesome cereals.

Cereal or grain is a member of the grass plant family, with starchy seeds used for food. Common cereals are: wheat, rice, rye, oats, barley, corn (maize), and sorghum.

Will Keith Kellogg
Will Keith Kellogg was the founder of the W.K. Kellogg Foundation, founded in 1906. In 1894, Kellogg was trying to improve the diet of hospital patients. He was searching for a digestible bread substitute using the process of boiling wheat. Kellogg accidentally left a pot of boiled wheat to stand and the wheat became tempered (soften). When Kellogg rolled the tempered or softened wheat and let it dry, each grain of wheat emerged as a large thin flake. The flakes turned out to be a tasty cereal. Kellogg had invented corn flakes.

Source: inventors.about.com.