What's hot and what's not in the 21st century? Using concept cars exhibited at the Tokyo Motor Show, consumers should expect an even heavier emphasis on small, clean-burning cars, which in many cases sport some rather unusual designs. Here's a preview:

Fuya-jo

Fuya-jo "rocks like a town that never sleeps and rides with the ease of a skateboard," says Honda Motor Co. of its "24-hour amusement zone." The concept car offers semi-standing seats, a steering wheel shaped like a turntable and an instrument panel laid out like an emcee's mixer.

Pistachio

One of Mitsubishi's newest prototypes, the Pistachio, gets up to 68 mpg in city driving because of its unique stop-start engine that automatically stops when the car does. It starts up again when the driver hits the gas pedal.

RX-EVOLV

Mazda engineers were challenged to design a four-door sports car. They came up with the RX-EVOLV. In addition to seating four comfortably, the car employs advanced cockpit technologies, such as an ID access card, a shift mode selector and a one-touch parking brake.

Kai

Isuzu says its Kai has taken the design of sports utility vehicles to new heights. The special exhibition vehicle came equipped with a V6 diesel engine, a newly developed suspension and new shock absorbers.

XVL

Nissan calls XVL its next-generation sedan. According to company literature, the concept model features a direct-injection, 3-liter gasoline engine mated to EXTROID CVT, the latest of Nissan's continuously variable transmissions.

Open Deck

Toyota calls its Open Deck a "dreamer's paradise" due to its voluminous space, innovative doors and open deck. The company says drivers can stamp their own individuality onto this concept model.