3. Fireflies: The flashing of fireflies is a striking example of synchronization in nature. In some areas of Southeast Asia, thousands of fireflies will gather at night in trees and flash on and off in unison. Certainly, they don't start flashing in unison; they go into the trees at dusk, and gradually sync up as the night progresses. To sync, the fireflies influence each other with their flashes: when one sees a flash, it slows down or speeds up in order to flash more closely in phase on the next cycle. Interestingly, if a human flashes a flashlight periodically, the fireflies will try to sync up with it. However, fireflies can only flash within a range of rates, so if the human flashes the flashlight to quickly or slowly, the fireflies will be unable to match the flashlight.