Take a look behind the scenes of the National Geographic documentary film 'Free Solo', which chronicles Alex Honnold's unbelievable free-solo climb up El Capitan. He is the first person to summit the near-vertical 1,000-metre (3,000-foot) face without any ropes or safety gear. National Geographic caught up with Honnold as well as co-directors Jimmy Chin and Elizabeth Chai Vasarhelyi at the film's premiere in New York.