UK Engineering and Physical Sciences Research Council (EPSRC) (EP/P030017/1); European Union’s Horizon 2020 Marie Skłodowska-Curie Actions (MSCA) (707084)Optical clearing is emerging as a popular approach particularly for studies in neuroscience. However the use of corrosive clearing solutions typically requires sophisticated objectives or extreme care with optical components chosen for single- or multi-photon imaging. In contrast to the use of complex, custom-made microscope objectives, we show that the use of a corrected multimode fibre (MMF) offers a route that is resistant to corrosion, can be used in clearing media, is not constrained by the refractive index of the immersion medium and offers flexible working distances. Using a correct...