Rainbows are just to look at, not to understand .. are not they? This category contains visualizations of topics so complex that it was not possible for use to write proper introductory material. We think the articles are still usable, as apart from applets, they contain links to the sources that may help to understand the subject if really required. Or you can just play with them, as children do with the Mandelbrot set. Maybe this is also useful, who knows.