Limits of Tree Branching
A single stem branches in two, then each branch in turn branches in two, and so on. At each step, the tips of the new branches have the same geometrical relationship to the previous branch as the first branches had to the original stem. Each dot represents the tips of branches. Vary the position of the first branch, and see the radically different limiting shapes produced.
This is related to a model of leaf shapes, as well as being an interesting piece of pure mathematics.