Could you design and build the world's most fuel-efficient car if you knew there was a $10 million payoff in the end? More than 60 teams of people in nine countries have taken on the challenge, hoping to reach new levels of fame and fortune.

The Automotive X Prize competition is offering up the prize to the team who can create a car that boasts a new record for fuel effieciency and according to the contest organizers, the wining entry will have to be innovative, but practical. The contest is aiming to see cars that can break the 100 miles to the gallon mark, but that can also be feasibly introduced to the market. Other tests the winning cars will have to pass include weather and terrain conditions, traffic and a cross-country race to determine speed and distance capability.

"We're not talking about concept cars," said Peter Diamandis, chief executive of the X Prize Foundation, at the event to mark the launch of the competition at the New York auto show. "We're talking about real cars that can be brought to market."

Contenders in the competition include a team from Cornell University, a high school from Pennsylvania and Tesla Motors, the start-up electric car company founded by Elon Musk, the brains behind PayPal.

Hit the jump to learn more about the Automotive X Prize.

» Reuters Environment