PKmito RED (also known as PKMR) is a bright, photostable, non-phototoxic mitochondrial probe based on the PKmitoâ„¢ dyes developed in the lab of Zhixing Chen at Peking University. PKmito RED labels mitochondria in live cells with very high specificity. The unique and unmatched feature of PKmito 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 RED accumulates in the mitochondrial inner membrane (IM). It allows imaging mitochonridal cristae structure and dynamics by STED superresolution microscopy using a 660 nm depletion line. PKmito RED does not require any genetic manipulation, transfection or overexpression of fluorescent proteins. PKmito RED enables multicolor imaging with SPY505, SPY620, SPY650, SPY700, SiR or GFP. It can be used for widefield, confocal, SIM or STED imaging in living cells and tissue.