ExM of mouse brain circuitry. The expansion of the Brainbow-expressing mouse hippocampus. A, Low-magnification widefield fluorescence imaging showing immunostained mouse hippocampus expressing virally delivered Brainbow3.0. B, Postexpansion widefield image of the sample in panel A. C, Maximum-intensity projection of high-resolution confocal microscopy stack following expansion of membrane-labeled Brainbow3.0 neurons from the boxed region in panel B. D, Pre-expansion confocal image showing one optical section of the boxed region in panel C. E, Postexpansion image of the same boxed region. ExM enables fine processes such as axons, which are not easily distinguished in dense neural circuitry (D), to be easily distinguished and traced (E). Scale bars: A, 500 μm; B, 500 μm (1,980 μm physical size); C, 5 μm; D, 5 μm (19.8 μm physical size), and E, 50 μm (198 μm physical size). Adapted from Tillberg et al. (2016).