Photos: Tomorrow's cars rally in Tokyo

Among the automakers showing off fuel cell vehicles at the Tokyo show is DaimlerChrysler, whose protoype line includes the sleek Mercedes F 600 Hygenius concept car. The Hygenius' high-voltage battery and hydrogen tank are located beneath the passenger cell, and its electric motor has been built into the rear-axle carrier.

Fuel economy isn't the only thing on the mind of car designers. Honda's six-passenger WOW concept wagon has a wooden floor and also functions as a kennel on wheels.

Seats in the middle of the WOW can be reconfigured into a dog carrier.

For dog lovers who want to keep a closer eye on Fido, the glovebox also packs a pooch. Take a bow, WOW.

The Pivo, from Nissan, is an electric car with a bubble-shaped cabin that rotates 360 degrees. If you get stuck in a tight spot, just spin the cabin and head back the way you came.

The interior of the Pivo keeps things simple. And very, very red.

Toyota has a different take on turning on a dime--its Fine-X has four independently steered wheels that enable it to rotate on the spot. Powered by a fuel cell hybrid system, it also has gull wing side doors that open upward.

The I-swing from Toyota is a one-seater running on three wheels--and two when in slow mode. "In addition to the stick control, a pedal control can be used to provide a fresh cornering feeling, as you shift your body weight as if you were on skis," Toyota says.

Mazda's Premacy Hydrogen RE Hybrid is a minivan concept whose power unit combines a dual-fuel, hydrogen/gasoline rotary engine and an electric motor.

The dual-fuel system in this RX-8 from Mazda enables a driver to select gasoline or hydrogen by simply flipping a switch. The Japanese carmaker plans to make this vehicle available for lease soon.