This simple, yet interesting experiment that was first described by Elizabeth Sumner Walter in 2001. She merely had students pour water into a dish containing some Gobstoppers candies.
Have you seen the new Crayola Crystal Effects Window Markers? You can draw on windows with these markers. Better yet, you can use these markers to teach students some chemistry! After drawing on a window with these markers and waiting a little while, the marker ink appears to crystalize! Check out the video.