Bread and cereals have a long history. The first bread was made in the Nile valley about ten thousand years ago. The people used stones to crush the grain into coarse flour, and then they made the flour into primitive forms of bread. Primitive bread was not like the bread we know today, because it was simply flour dough dried on heated stones. The invention of ovens came later. Levin breads and cakes, which are made to rise by the action of yeast, were also a discovery of the ancient Egyptians. The Egyptians were the first people to master the art of baking. News of this new wonder food spread to other places in the Middle East. Soon, other people were collecting seed, cultivating land and inventing ways to turn grain into flour. Baking used to be a social activity. While some homes had their own ovens, many families had to bake their dough and communal bakeries to identify their loaves. Each household would make a distinctive mark on the bread, sometimes with a special stamp bearing the family.