Stochastic optical reconstruction microscopy (STORM) image of microtubules and clathrin-coated pits. Credit: Xiaowei Zhuang

After the grandfather of modern microscopy Ernst Abbe formulated the theories that revolutionized modern microscope design, the imposed limits on the spatial resolution were considered inviolable. Over the past decade clever microscopists have devised ways to break these limits in fluorescence microscopy, but the need for specialized equipment inhibited uptake of super-resolution optical techniques. In the past two years the situation has changed dramatically.

First, it is now possible to purchase a microscope from a major optical company that can implement one of these techniques such as stimulated emission depletion (STED) or 4Pi microscopy. Second, several groups have described methods for super-resolution fluorescence imaging that only require a commonly available microscope, specialized but easily obtainable fluorescent labels, and clever microscope control routines and data processing.

These methods operate by stochastically switching individual fluorophore labels back and forth between fluorescent and nonfluorescent states or between two different colors. This allows the precise location of individual fluorophores to be determined. The methods can theoretically provide the exact location of every labeled protein in the cell at resolutions close to the size of proteins themselves.

Whereas the first reports of these methods used fixed samples and a single label, 2007 saw the development of multicolor versions and application to living cells. We look forward to continued development of these stochastic imaging techniques to further improve their performance and simplify their implementation. Even methods like STED can be and have been simplified, and methods based on new technologies with unique capabilities are likely to be developed.

Super-resolution optical imaging is still only providing a trickle of novel biological results, but this situation should change quickly.