CELS-3D-Cutting edge light source for exciting fluorescence in microtome-based 3D microscopy and targeted correlative microscopy.

We discovered that the light entering a triangular ultramicrotome glass knife from the bottom exits the knife through its cutting edge, forming an oblique light sheet illumination suitable for imaging. We adopted this light sheet for side illumination of the sample blocks during sectioning on the ultramicrotome, for 3D imaging, and for targeting fluorescent features for confocal-, electron- and correlative microscopy. In this paper, we present a working prototype named CELS-3D (Cutting Edge Light Source, Three-Dimensional), a microscope mounted on an ultramicrotome.