Celebrated physicist Stephen Hawking knows more about the universe than almost any other person ever to walk the planet, but some answers still escape even him.
When asked by ABC News' Diane Sawyer about the biggest mystery he'd like solved, he said, "I want to know why the universe exists, why there is something greater than nothing."
Other topics covered include: how Hawking reconciles the idea of religion and science; and what he considers the best and worst decisions of our generation.
So, watch this video as the physicist discusses everything from the universe to family.
Here is more from Diane Sawyer's interview with Stephen Hawking.
Here is a picture showing Hawking trying out Zero Gravity.
