An eight-day mission has turned into a nine-month space stint for two NASA astronauts who are finally set to come home. But why have they been away for so long - and what are the effects of such a lengthy stay in space?

As we plan longer missions to space, the moon, Mars, and beyond, we'll need a way to keep our astronauts fed when they can't get resupply packages from Earth. That means figuring out how to grow food in space.