Synthetic biology
Synthetic biology is a new field that aims to understand biological systems by re-engineering them and designing and building new ones. The cost of DNA synthesis is dropping rapidly and our ability to construct new genes with new functions is increasing rapidly. You can find out more about the field in these review articles:
Synthetic biology: new engineering rules for an emerging discipline,Andrianantoandro, Basu, Karig, and Weiss,Nature Molecular Systems Biology, 2006 (PDF)