Paul Tillberg, now a Janelia Fellow at the Howard Hughes Medical Institute Janelia Research Campus, developed the protocol for expansion microscopy with colleagues Ed Boyden, currently a professor at MIT, and Fei Chen, currently a Core Institute Member at the Broad Institute. The method exploits the fact that biological tissue is mostly water, and it is this watery fraction, Tillberg explains, that is replaced by a “swellable hydrogel” that expands the sample to sizes that make it much easier to image with familiar fluorescent tags and standard light microscopy equipment.