Mahiro Nakabayashi (then a third-year doctoral student in the Graduate School of Science and Engineering, graduating March 2026) and Professor Shotaro Hayashi (Faculty of Engineering) at Kochi University of Technology have revealed that the "hierarchy of intermolecular interactions" (i.e., the order of bonding) in organic molecular crystals determines their crystal structure, luminescent properties, and even phase transition behavior. Previously, when multiple interactions coexist between molecules, it was considered extremely difficult to predict and control which force would take precedence and how it would govern the whole. This research has been highly acclaimed academically for proposing a new guideline: "design molecules with a priority order (hierarchy) in the strength of forces, enabling precise control over crystal properties and their changes in response to stimuli." This achievement was published on June 30, 2026, in Angewandte Chemie International Edition, an international academic journal with high impact in the field of chemistry. [Key Research Findings] Revealed that in organic molecular crystals, the "types" and "strength hierarchy (hierarchy)" of forces that attract molecules to each other (intermolecular interactions) determine the crystal's behavior. Discovered that by designing molecules based on the aforementioned "order of bonding," it is possible to create two different crystals (polymorphs) emitting yellow and green light, respectively, from the same molecule. Successfully visualized changes in crystal state through different processes as changes in emission color, depending on whether heat (thermal stimulus) or rubbing (mechanical stimulus) was applied. To explore future application possibilities, demonstrated the application by creating "security paper" that changes its emission color to yellow when rubbed after being impregnated with the molecule, and can be erased (reset) by heating. ▲Figure 1 Security paper created. Changes in color due