Two men attempt 'world's hardest rock climb'

Video caption, Watch Martin's report on the two climbers

Two daring adventurers are roughly halfway through what's been called the hardest rock climb in the world!

Tommy Caldwell and Kevin Jorgeson are going up the Dawn Wall of El Capitan - a 900m high rock formation in California's Yosemite National Park.

They're free climbing which means they're just using their hands and feet to get up, with ropes only being used as a safeguard against falls.

They hope to be finished by Friday.

Many people have climbed the Dawn Wall before, but what makes this challenge special is that the pair would be the first to do it free climbing in this way.

And even when they're not climbing it's no easy feat - the two men have to sleep in sling tents suspended from the wall!