The National Geographic Glow-in-the-Dark Crystal Lab is an easy and fun way to grow a crystal at home that glows in the dark! fun way to grow a crystal at home that glows in the dark! Simply mix the crystal-growing powder in water, add your seed rock, and in just a few days you’ll have an amazing crystal! Fast-growing crystal-growing powder results in a crystal in as little as 3 days. Seed rock is the glow-in-the-dark element, the crystal itself is white.