During muscle differentiation, mitochondria undergo dramatic changes in their morphology and distribution to prepare for the higher rate of energy consumption. By applying a mitochondria-targeted rosamine library in C2C12 myogenesis, we discovered one compound that controls muscle differentiation. When treated to undifferentiated myoblasts, our selected compound, B25, inhibited myotube formation, and when treated to fully differentiated myotubes, it induced fission of multinucleated myotubes into mononucleated fragments. Compared to myoseverin, which is known for inducing myotube fission by destabilizing microtubules, B25 affects neither microtubule stability nor cell cycle. Further investigation identified that B25 induces myotube fission ...