When I was a kid, my favorite science toy was a box of "Magic Rocks," those things that made little stalagmite-style spires in water. (A close second was Grow-a-Frog, which was exactly what it sounded like.) But also fun was anything involving growing crystals, including the "Magic Tree," in which capillary action draws liquid up a cardboard tree cut-out, forming weirdo fuzzy-looking crystals. Half of the magic was checking in on the tree every five minutes to see if anything had changed...then falling asleep and seeing it in the morning, when it had fully "grown in."
In this short video, Steve Spangler shows you how to make a a Magic Crystal Tree at home using (mostly) household ingredients. (The only ingredient I don't have on-hand is bluing, but that's actually not too hard to find -- even Amazon carries it.)
So here's the instructional video, just over a minute long:
For a text-driven walkthrough, check out Spangler's page on this project. It also explains the science behind the project as well.
And now, the inevitable time-lapse videos of magic trees growing: