Mitochondria are the powerhouse of the cells and generate energy in the form of ATP. Mitochondria utilize oxidizable substrates to produce a membrane potential in the form of a proton gradient across the mitochondrial inner membrane. Mitochondrial membrane potential is tightly interlinked to many mitochondrial processes, including ATP synthesis, ROS, calcium sequestration and import of proteins into the mitochondrion. Therefore, pharmacological changes in mitochondrial membrane potential are associated with several pathological parameters. BioVision’s TMRE Mitochondrial Membrane Potential Assay Kit uses TMRE (tetramethylrhodamine, ethyl ester) to label active mitochondria. TMRE is a cell-permeable, positively-charged, red-orange dye that readily accumulates in active mitochondria. Protonophores like FCCP and CCCP induces dissipation of mitochondrial membrane thus results in compromised staining.