Light under compression The ability to confine light to volumes much smaller than the wavelength produces high electromagnetic fields that can then be exploited in chemical and biological sensing and detection applications. Using silver nanocubes placed on a graphene surface, Epstein et al. developed a single, nanometer-scale acoustic graphene plasmon cavity device that can confine mid-infrared and terahertz radiation with mode volume confinement factors of 5 × 10 ^–10 . With the response being dependent on the size of the nanocube and electrically tunable, the results demonstrate a powerful platform with which to develop sensors in what has been a challenging wavelength regime where molecular fingerprints reside. Science , this issue p. 1219