Quantifying Expansion Microscopy with DNA Origami Expansion Nanorulers

In the past decade super-resolution microscopy 1,2 developed rapidly and allowed seeing new structural details in fluorescence microscopy, especially in the field of bioimaging Most of the evolving techniques like (d)STORM 7,8 , STED 9 or SIM 10 -just to name a few -focused on overcoming the diffraction limit 11 by increasing the technical resolution of the microscope, often in combination with specifically designed probes, for example by using blinking fluorescent dyes But the approach to improve the effective microscope resolution of a system is not the only way to reveal new insights. An alternative approach is based on physically expanding the sample to increase its size by a multiple and to subsequently image the sample by conventional fluorescence microcopy. The technique termed expansion microscopy (ExM) allows effective resolution below the diffraction limit and therefore directly complements and competes with established super-resolution techniques, but offers the advantage to use standard confocal or wide-field microscopes.