The first announced Nobel prize of 2006 was for work in medicine/physiology, recognising work done in the field of genetics. We had thought that we had all the basics down pat as far as genetics is concerned, when along came the lowly petunia to shake us out of our complacency. It turns out that tiny bits of genetic material (small RNA) can silence genes even after the gene has been read-off on its way to being expressed by a cell. Even more surprising was that the same basic 'silencing' mechanism is also active in animal cells.
The implications are enormous. On the one hand there is now potential to externally modify individual gene expression and that will have a lot of bearing on treating some sorts of genetic diseases. On the other hand, individual gene action can now be much more easily studied helping us to make sense out of the massive amount of data that became available when entire genomes have been sequenced.