Glow in the dark dice sets are quite possibly the pinnacle of awesomeness in gaming. Back in the old days of hand-numbering our dice with crayons gamers would have given up their first born for this kind of awesome. The fact that we can now buy glow in the dark D&D dice proves that technology is serves us, rather than the other way around. At least until the robot uprising, anyway.
Glow in the dark dice are perfect the perfect gaming dice for playing those atmosphereic RPGs. Call of Cthulhu and other horror or mystery games just plain work better with the lights down dim, or playing by candlelight for old-time era games, or even playing by blacklight or red or blue lights for creepy sci-fi or futuristic games. When you buy glow in the dark dice , you'll no longer have to wonder where your dice are when they fall off the table, or use a flashlight to actually read the numbers to determine whether your character has died, or just gone insane.
These dice glow due to the kind of plastic used. In the light these dice typically look like a sort of light yellow-green, though some do come in different colors, in which case we'll also have a picture of what they look like in the light (you can find this under the "additional images" tab on the product page. These dice are "charged" by sitting in the light for a time, the brighter the better. They will then glow brightly in the darkness, and the intensity of the glow will slowly fade over time. Typically these dice will have numbers inked on that will appear dark against the glowing surface of the dice regardless of the color of the numbering, but there are also glow in the dark dice where only the spots of the dice are made from glow material, in which case the dice are as dark as anything else without light, and you just get the glowing spots.
For whatever reason, not a lot of manufacturers produce glow in the dark dice, and those that do tend to make primarily six-sided dice that glow. We're always looking for more glow in the dark options, and the day we can finally find a good 7-dice glow set that is also inked that we can put online, we'll be happy gamers indeed.