Small things bright and beautiful: Single molecule fluorescence detection

Single molecule detection has become instrumental in our understanding of the molecular world. The ability to perform experiments molecule by molecule and probe directly the static and dynamic disorder in a system has revealed new insights into a range of fundamental problems in physics, chemistry, and biology. These insights are now laying the foundations for engineering devices such as optical switches and photonicwires at the molecular level. Of the many single molecule techniques available, fluorescence microscopy has proved an invaluable tool by virtue of its high sensitivity, time-resolution, noninvasive nature, and compatibility with other spectroscopic techniques. The development of specific detection modalities has allowed amultitude of previously impracticable experiments to be realized, fromphoton antibunching to single particle tracking in living cells. Advances in fluorescent probe design, detectors, modes of acquisition and data analysis will undoubtedly push single molecule techniques to new limits of sensitivity and into new areas of application.