“In the field of molecular fluorescence, researchers have synthesized a perylene diimide derivative, PDI-COOH, which exhibits enhanced fluorescence when combined with calcium ions in THF/H2O solution. By studying the assembly and fluorescence behavior under different hydration states, they proposed the fluorescence emission mechanism of PDI-COOH/Ca2+, revealing a novel strategy for aggregated state fluorescence enhancement and highlighting the crucial role of water in molecular fluorescence emission and assembly.”