The MitoView™ Fix 640 is a far-red fluorescent live-cell mitochondrial stain. The nontoxic, cell membrane–permeant dye Methyla accumulates in the mitochondria of live cells and has a reactive group that covalently attaches to proteins inside the mitochondria. This reportedly results in stable mitochondria staining that lasts for days in live cultures, is well retained after fixation with formaldehyde or methanol, and withstands permeabilization. The company claims staining with MitoView™ Fix 640 shows better specificity after fixation compared to MitoTracker® Deep Red and other mitochondrial stains currently available. MitoView™ Fix 640 is offered in 1 or 10 units of 50 μg.