A single molecule is ridiculously tiny, about 1 nanometer, roughly 100,000 times smaller than the diameter of a human hair. Yet individual molecules rule the nanoscale activity and structure in our cells. Thirty years ago, single molecules were first detected optically, but how do we really detect a single molecule today, and what good is it? It is an amazing fact that you can even detect single molecules with your own eyes. When a new regime of science is breached, surprises often occur: single molecules show amazing dynamics, blink on and off, and can be controlled by light. Far from being only an esoteric effect, these “switching properties” of molecules can now be used to obtain “super-resolution” to see the tiny nanoscale structures inside cells. Essentially, with tiny single-molecule light sources decorating a structure, the on/off process is used to light up only subsets at a time. A pointillist display then reveals the hidden nanometer-scale structure, opening up a new frontier for understanding and applications. Even the key RNA molecules of a coronavirus infection look like galaxies inside infected cells! Single molecules can also help improve the information available from electron microscopy images by answering the question: “Where is my protein?”

W.E. Moerner is a physical chemist who won the 2014 Nobel Prize in Chemistry for the development of super-resolved fluorescence microscopy. He is the Harry S. Mosher Professor of Chemistry and Professor, by courtesy, of Applied Physics at Stanford University.

https://chemistry.stanford.edu/people/w-e-moerner