Polydiacetylene (PDA) is a “chameleon molecule” that instantly changes its color or fluorescence in response to external stimuli such as force, temperature, or molecular binding. At the Sugihara Lab, we push this unique property to its limits, creating innovative sensors that can visualize friction and pressure, as well as simple diagnostic tools for detecting infectious diseases. PDA technology, which conveys invisible phenomena through vivid color changes, is paving the way for the next generation of intuitive sensing.