A rapidly growing technology in the watch industry, “gaseous tritium light sources” (GTLS) bring dial faces to life by way of their signature glow. Free of electricity, this modern solution enacts a low-intensity form of radioluminescence, conjuring seamless legibility. There’s no trigger needed and the effect lasts for up to 12 years at a time. GTLS watches are perfectly safe to use and the electrons emitted from tritium gas can barely penetrate the air. Even if you were to break the watch and absorb all the gas, you’d be (reportedly) taking in a harmless dosage.