“…In contrast to the visual appearance of common colorants, such as pigments and dyes, the nonbleachable structural colors arising from Bragg optical diffraction can be tuned throughout the entire visible spectrum by adjusting the spatial arrangement and effective refractive index of photonic crystals. To tune the structural colors on demand, diverse stimuli-responsive mechanisms are coupled with the photonic structures to convert external stimuli into optical responses either permanently or reversibly. − Among these stimuli, the electrical stimulus has drawn plenty of interest due to its low operational current/voltage, high electrical tunability, and rapid response time. Accordingly, electrically responsive photonic crystals can be a promising candidate for various practical applications, including displays, anticounterfeiting materials, army camouflage, security devices, optical filters, chemical/biological sensors, and interactive wearable devices. − …”