CNN Presents: Searching for Extreme Lifeforms in Yellowstone

Besides Chile's Atacama Desert and Mars, the television documentary CNN Presents recently visited Yellowstone while filming a story on the search for life in the world's most extreme environments.

Check out the photos and video on the website.

The search for life in space has always been the stuff of science fiction books and movies. But from the harshest deserts of Earth to the far-flown depths of space, scientists are looking for that elusive sign that we are not alone...