I5M: 3D widefield light microscopy with better than 100 nm axial resolution.

Sevenfold improved axial resolution has been achieved in three-dimensional widefield fluorescence microscopy, using a novel interferometric technique in which the sample is observed and/or illuminated from both sides simultaneously using two opposing objective lenses. Separate interference effects in the excitation light and the emitted light give access to higher resolution axial information about the sample than can be reached by conventional widefield or confocal microscopes. Here we report the experimental verification of this resolution performance on complex biological samples.