Top 10 Unsolved Mysteries Of Science

Scientists don't understand everything about the ways of the Universe. Physicist Brian Cox once said: 'I'm comfortable with the unknown - that's the point of science. There are places out there, billions of places out there, that we know nothing about. And the fact that we know nothing about them excites me, and I want to go out and find out about them.'
So what are some of the top mysteries keeping scientists busy?
Here's a top ten of unsolved mysteries.