Termites provide us with an excellent example of emergent
behavior: stacking woodchips. How do they do it? Actually, it's pretty simple.
Each termite roams around randomly until it finds a woodchip. It picks up the
chip and resumes random roaming until it finds another woodchip. It then drops
the woodchip it is carrying and goes off to look for another woodchip. Pretty
soon, we have piles: