Water mills are structures that use the energy of flowing water to perform work, typically grinding grain into flour. They consist of a water wheel that turns when water flows over it, converting the kinetic energy of the water into mechanical energy. This energy can then be used to power various machines. Historically, water mills played a crucial role in agriculture and industry, especially before the advent of electricity. They were often built near rivers or streams to take advantage of the constant water flow. Water mills are an important part of the history of technology and are often associated with the Industrial Revolution.