We report the development of a modular and optimized thin-sheet laser imaging microscope (TSLIM) for nondestructive optical sectioning of organisms and thick tissues such as the mouse cochlea, zebrafish brain/inner ear, and rat brain at a resolution that is comparable to wide-field fluorescence microscopy. TSLIM optically sections tissue using a thin sheet of light by inducing a plane of fluorescence in transparent or fixed and cleared tissues. Moving the specimen through the thinnest portion of the light sheet and stitching these image columns together results in optimal resolution and focus across the width of a large specimen. Dual light sheets and aberration-corrected objectives provide uniform section illumination and reduce absorption artifacts that are common in light-sheet microscopy. Construction details are provided for duplication of a TSLIM device by other investigators in order to encourage further use and development of this important technology.