Drawn from the medicinal flora Toddalia asiatica's fluorescent root (Figure ), employed traditionally for treating ailments such as rheumatoid arthritis and wound injuries, the coumarin structure offers a potent source of fluorescent molecules. Inspired by this, Wang et al. designed two AIEgens named 5-MOS and 6-MOS . The restrained intramolecular motion (RIM) mechanism can well explain AIE performance (Figure and). The two adjacent alkoxy groups of 6-MOS are repel to each other and distributed on the upper and lower sides of the central conjugated benzene ring plane with different twisting angles. According to theoretical calculations, the energy distribution of the conformations indicates that the energy is highest when twisted into a coplanar conformation, indicating an unstable state. Conversely, the energy decreases when the conformation is on the two sides. As an additional note, the weak fluorescence of 5-MOS in an aqueous environment could be activated when it enters cellular mitochondria, aiding its application in wash-free mitochondria imaging in cells.