A windmill's function is to harness the power of the wind to generate useful energy for humans. In the past, people used this energy to grind grain or pump water. More modern windmills turn wind energy into electrical power.
People in ancient China used windmills to pump water, while Persian and Middle Eastern farmers and merchants used vertical windmills to grind grain. Brought back to Europe after the Crusades, the windmill caught on quickly, becoming an integral part of the economy. The most famous windmills were in the Netherlands, where people used them to grind grain and to drain lakes and marshes. Dutch innovators created the modern wind turbine to generate electricity in the 1890s. Since then, scientists have made wind turbines that generate as much power in some regions as fossil fuels do, making them the fastest-growing source of energy in the world, according to the Department of Energy.