The windmill was an invention from the Middle Ages that was truly ahead of its time. During the Middle Ages, most people in Europe consumed large amounts of wheat and oat for food. After the wheat was harvested, it had to be turned into grains to make bread (dough) and porridge. However, turning large amounts of wheat into grains required a lot of manual labor. Unfortunately, as the population of Europe grew, there wasn't enough manual labor to keep up with the supply of grain production. Therefore, the windmill was created to turn massive amounts of wheat and oats into grains. The windmill relied on sustainable energy - wind - to rotate its massive mechanical parts to transform wheat into grains for consumption. Without the windmill, many Europeans would have gone hungry from a lack of grain.