Do you have a budding scientist in your house? I do! We recently picked up a $1 crystal growing kit from Family Dollar. I had purchased one from a name brand company a while back and it did not grow. My scientist was very disappointed! I had no hope that this kit would work because it was so inexpensive, but I bought it for him anyway.
See the results below! This is at about a week later. The liquid had already evaporated and the crystals on the bottom of the tray started to burst upward. The ones on the rocks were pretty much done growing. It even came with the little rocks.