Food - How can we ensure everyone has healthy, sustainable food?

If you had the chance to solve a big problem in the world, what would it be?

The Longitude prize is a huge science challenge and voting is taking place to decide which of six big world problems people should tackle for a chance to win £10million.

This week we're looking at the 6 possible including how to provide everyone with healthy, sustainable food?

Nel's been taking a look...