"This is an open question: What is this fractal? It's a method for filling a 2D plane with circles in an orderly way - circles made of circles, all the way down. There are published examples of similar systems, like the Apollonian Gasket, the Kleinian Groups, Indra's Pearls, but I've never seen this particular arrangement before, and I've been looking for over ten years." - Ňicķ from Bookmarklet