Climbers Tommy Caldwell and Kevin Jorgeson have spent seven years studying, planning, and practicing to be the first people to ever free climb El Capitan's Dawn Wall, a 3,000 foot vertical wall that's about as smooth and difficult a free climb as exists in the world. Anticipation is that they'll complete this climb of historic significance in the next few days, perhaps as early as Wednesday.
Some background for non-climbers like myself:
After a week of living on the wall in portaledges—dodging falling blocks of ice each morning and sustaining frigid winter conditions with nighttime temperatures plummeting below freezing—Kevin and Tommy are more than halfway there. As of Friday, January 2, both climbers have freed each of the route’s first 14 pitches, which constitute the bulk of the hardest climbing.
A long “multi-pitch” rock climb, such as the Dawn Wall, is broken down by the belays—the places on the wall that provide good stances on ledges where climbers can stop and belay each other. The individual pitches are the paths that link these points of belay, and this is where the actual rock climbing takes place. On this ascent of the Dawn Wall, Tommy and Kevin have the goal to climb each pitch, in succession, without falling and without returning to the ground in between. If a climber does fall, he must return to the previous belay, pull the rope down with him, and try again to complete the pitch without falling.
The reason it's taken seven years of planning is that the climb is so difficult that Caldwell has had to study the wall in minute detail to find features in the contour to serve as handholds or footholds and then link them together in a possible path up. This video gives you an idea of that process, including many gnarly falls and slips that left my palms sweaty (and yes, knees weak, arms are heavy).