PKmito DEEP RED (also known as PKMDR) is a bright, photostable, non-phototoxic mitochondrial probe based on the PKmitoâ„¢ dyes developed in the lab of Zhixing Chen at Peking University. PKmito DEEP RED labels mitochondria in live cells with very high specificity. The unique and unmatched feature of PKmito DEEP RED is its extremely low phototoxicity, due to the presence of the intramolecular triplet quencher cyclooctatetraene (COT) group. It allows to perform long term imaging of mitochondria without damaging them. PKmito DEEP RED accumulates in the mitochondrial inner membrane (IM). It allows imaging mitochonridal cristae structure and dynamics by STED superresolution microscopy using a 775 nm depletion line. PKmito DEEP RED does not require any genetic manipulation, transfection or overexpression of fluorescent proteins. PKmito DEEP RED enables multicolor imaging with SPY505, SPY555, SPY595, SPY620, GFP or mCherry. It can be used for widefield, confocal, SIM or STED imaging in living ce