Biological and chemical substances can be rapidly detected in real-time for public health and environmental monitoring purposes. In a new report now on Science Advances, Inki Kim and a research team in mechanical engineering, materials science and electrical engineering in the Republic of Korea and in Pakistan proposed a compact sensor platform to integrate liquid crystals (LCs) and holographic metasurfaces to sense the existence of a volatile gas, and then provide an immediate visual holographic alarm. The team combined the setup to form ultracompact gas sensors without complex instruments in order to detect gas via visual cues. The researchers proved the applicability of the compact sensors by integrating the metasurface-based gas sensor on safety goggles via a one-step nanocasting process.