Toyota's 1/X concept, shown at the 2007 Tokyo auto show, uses a body design that closely resembles that of the current Prius. But the 1/X has a lot of tricks up its sleeve that could give it double the already frugal Prius' mileage. First off, the 1/X's body is made of the same carbon fiber materials Toyota developed for its racing cars. This type of body makes the 1/X a third lighter than the Prius. As a flexible fuel vehicle, the 1/X's plug-in hybrid power train can burn gas and ethanol. With its lightweight body and plug-in hybrid system, it can run for much longer distances than the Prius under electric power. Toyota took some radical steps with the platform, putting the engine and hybrid system under the rear seat, giving the 1/X rear-wheel drive and good weight distribution.