Each firefly fires in an oscillatory way with the same cycle but starts at a randomly different time in its cycle. When a firefly emits light, its neighbors are stimulated and they increase their internal clock time to catch up. As a result, they light up earlier than otherwise. It is shown that all fireflies are eventaully sunchronized in firing, and light up at the same time. (Synchronization takes a while (about 20 - 40 seconds).)