You have to realize that, about 20,000 years ago, there was a cataclysmic event when an entire rock face collapsed and sealed off the cave. It's a completely preserved time capsule. You've got tracks of cave bears that look like they were left yesterday, and you've got the footprint of a boy who was probably eight years old next to the footprint of a wolf.

In a way, I managed to get the deepest things, the best things out of people. That's why I'm a filmmaker. If you don't have it in you, you'd better do something else.

When we speak about trespassing, we speak about artistic trespassing. You have to be prudent and have common sense and a sense of responsibility when you're trespassing. I think you haven't seen a film on volcanoes like that before. It's not National Geographic. It is wildly imaginative and very poetic and has a sense of awe that you normally do not see in films.

You also can understand how to play tennis from Serena Williams, and she is awesome. I haven't seen her Masterclass but just watching her on the court - I saw some of Wimbledon on TV and there's such an awesome force in her and focus and determination and technique, you just look at her and it's awesome. If I would like to learn tennis I would immediately turn to her.

Roger Ebert was a very valiant soldier of cinema who passed away, and we miss him. It's over with serious discourse about cinema in the print media and on television. It has been replaced by celebrity news. So we are speaking in his spirit always.

I couldn't roam wildly and speak secretly with villagers [in North Korea]. No way you could do that. And honestly, I didn't even try. I was realistic of what I could do and yet persuaded them into accepting numerous things that I shouldn't have filmed.

I am somebody who creates images, with my perspectives, fascinations and my instincts as a narrator. You have to activate the audience's imagination. If you are just giving them scientific results, they would forget the film in five minutes flat.