Dapi-Fluoromount-G is a water-soluble, instant-blue nuclear probe fluorescing (455nm) compound for mounting fixed slides using a staining procedure having an aqueous final step. Mounting slides with Dapi-Fluoromount-G stains the cell nucleus and may also reduce fluorochrome quenching during analysis of slides by fluorescence microscopy. This mounting medium also provides a semipermanent seal for long-term storage of slide preparations.