I grew up in a semi-rural town, where people had long gravel driveways spanning the massive acreage up to their homes. These driveways were almost never well lit, and sometimes if you weren't paying attention, you would trample the grass and possibly end up in a ditch. A batch of photo luminescent stones mixed in with the gravel would come in handy on those nights.
That's what Core Glow pebbles are. The pebbles are made of an aggregate of synthetic materials (basically a mashup of a bunch of different elements), resin and a hint of photo luminescent pigments. When exposed to sunlight, the pigments in the stone perk up and get excited. As day turns into night, the rocks emit an afterglow. They naturally illuminate a driveway to create a sparkling pathway that requires absolutely no electricity.
Because there are no wires and no bulbs needed for this source of light, these rocks, that seem better suited for an aquarium than a driveway, are completely carbon emission-free. The glow lasts for 10 to 20 hours and slowly fades as the charge wanes. The photo luminescent pigments on the rocks have been engineered to be waterproof, so even if a nighttime shower pops up, driveways will still be easy to find.
Completely necessary? No. Cool and extremely helpful in an area otherwise hard to light? Yes. Also, great conversation starter for out-of-town visitors.