(CNN) — Their challenge is the Dawn Wall.
Professional climbers Tommy Caldwell and Kevin Jorgeson are in the middle of tackling this most difficult of challenges at Yosemite National Park's El Capitan.
There are many routes up El Capitan, a 3,000-foot-tall granite monolith that has long beckoned thrillseekers. But only a handful have been attempted by climbers trying to free climb -- using only their hands and feet -- with ropes designed only to catch them when they fall.
A Yosemite National Park official confirmed that if they succeed, Caldwell and Jorgeson would be the first to successfully free-climb the smooth cliff face.
That's why Caldwell and Jorgeson have spent several years planning and practicing their climb, assembling a support team that helps feed and care for them as they make their way up the wall.
They chose to climb in winter so their hands won't sweat and there's more friction between their rubber soles and the rock. They relieve themselves in plastic bags. They sleep at night in pitched tents suspended on the wall, with Caldwell waking up twice per night to apply lotion to his hands.
They've already been on the wall for more than 10 days. If all goes well, the climb should take a total of two to three weeks.