Shining the spotlight on functional molecular complexes: The new science of single-molecule cell biology.

Single-molecule research is emerging as one of the fastest growing fields within the biosciences. Historically, most of the techniques employed have operated largely in the world of the test tube in which the components of the biological system under investigation have been extracted and purified from cells to reduce them to just the key ingredients under study, and this research has involved novel, pioneering methods of biophysics to obtain single-molecule measurements. What has emerged recently is the technical ability to now perform key single-molecule experiments whilst retaining the native biological context-namely to do single-molecule experiments on functional living cells. This presents essentially a new science of "single-molecule cell biology", which combines classical cell biology approaches with modern single-molecule biophysics. Here, key recent studies which have pushed back the boundaries of this field are discussed.