Photoisomerization is a structural change in a molecule caused by light. In some compounds, such as azobenzene, ultraviolet or visible light can switch the molecule between forms with different shapes and properties. That change can be reversible, which makes photoisomerization useful in light-responsive materials.
In cyber security, the term matters because hardware is not always purely static: light can act as an external control input. If a material’s electrical behavior changes after illumination, that can affect sensors, semiconductor films, optical components, or any system that depends on stable physical properties. Attackers may try to exploit wavelength sensitivity or exposure history to alter behavior, while defenders use the same knowledge to test for hidden state changes, environmental dependencies, and unexpected persistence. The key lesson is to treat “fixed” hardware with caution when light-sensitive chemistry is involved.