The idea to break the diffraction limit by using the this doughnut-shaped excitation spot comes from the STED microscopy (http://en.wikipedia.org/wiki/STED_micr

The idea to break the diffraction limit by using the this doughnut-shaped excitation spot comes from the STED microscopy (http://en.wikipedia.org/wiki/STED_microscopy http://en.wikipedia.org/wiki/STED_microscopy) developed by Stefan Hell (Max Planck Institute for Biophysical Chemistry in Goettingen, Germany). He actually showed that an additional intensity-dependent term can be added to Abbe's diffraction limit allowing sub 100um resolution with light. I think this idea is awesome and it sure won't be the last invention made possible by this trick.