 When you're first beginning you're sort of having to learn a lot of different things and you're not sure which thing you should be doing and you realize you can't do it all. I would tell them, don't worry about that too much. Just pick the thing that most excites you right now and sure it's true that you won't know what you might end up doing in five years or so but it really won't matter because over time you'll realize that first of all everything is connected to everything else and secondly you'll need, even if you change fields, you'll need to know those other things so you can talk to people who do those other fields. More and more what we're doing is integrated science of many different types. So just follow your own path, always choosing the thing. Don't postpone doing what you want to do. Do it right now and go as deeply into it right now as you can and if you need to make a change later and you will, I mean we all change. We never continue doing what we did 10, 20 years earlier so just make the changes as your interest changes and your opportunities change. Don't worry about making the absolute right decision that will work forever.