Zenodo hosts the archival version of this document; for convenient viewing, please visit andrewgyork.github.io/high_na_single_objective_lightsheet Abstract We describe how to design and build a module that converts a typical microscope into a high numerical aperture (NA) light-sheet microscope that uses only one objective at the sample. We intend it to be 'game changer' in the world of live cell imaging, greatly reducing phototoxicity without degrading image quality or breaking compatibility with existing sample preparation. Our method is compatible with coverslipped samples like slides, dishes and multiwell plates. The volumetric imaging performance is fast, gentle and high resolution, and the instrument is low cost and simple to align and maintain.