According to personal experience, Nixie Tubes are really awesome. My Divergence Meter Project made me realize that. But what were they exactly?
Basically a Nixie Tube was a type of Cold Cathode Display, so unlike most cathode displays ( e.g tungsten light bulbs ) they didn’t rely on heat to create their light, but instead it uses a process called glow discharge. Though of course this didn’t mean they stayed cool during their operation, if the current were to go over allowed ratings for prolonged times then it could potentially heat up the tube.