interesting reseach - (Jun/15/2012 )
You should ask and discuss it with your supervisors and perhaps other people working there (PhDs etc). It usually should be related to what the institute is working on / is specialised and what know-how, interests and equipment is available. E.g wanting to work on gene expression with a real-time approach is not fitting if nobody has such apparatus and they never worked with it...
If this is completely open, because you look for a place to work after finding a topic, you should have in mind in what you are interested in, because you have to work quite a lot of time and intensely on this. If you later realise that it's uninteresting for you, too complicated, or whatever then it might be too late.