Graphene has many properties; it is e.g. an extremely good conductor. But it does not absorb light very well. To remedy this limiting aspect of what is an otherwise amazing material, physicists resort to embedding a sheet of graphene in a flat photonic crystal, which is excellent for controlling the flow of light. The combination endows graphene with substantially enhanced light-absorbing capabilities. In a new study published in EPJ B, Arezou Rashidi and Abdolrahman Namdar from the University of Tabriz, Iran demonstrate that, by altering the temperature in such a hybrid cavity structure, they can tune its capacity for optical absorption. They explain that it is the thermal expansion and thermo-optical effects which give the graphene these optical characteristics. Potential applications include light sensors, ultra-fast lasers, and systems capable of modulating incoming optical beams.