Karting is type of motorsport with simple, four-wheeled, single-seater cars with two- or four-stroke engines cooled by water or air. They have tubular chassis and weigh between 70 and 150kg, depending on the model. There are professional championships all over the world, although the country with greatest influence on karting, and other areas of motoring, is Italy. Karting is often done for fun, as a hobby, not necessarily by professional drivers. It is normally considered a starting point for other motorsports, which are generally more expensive and complicated. It is known throughout the world for "training" well-known drivers in international categories, such as Aytron Senna, Alain Prost, Emerson Fittipaldi, Nelson Piquet, Michael Schumacher and many others.