Touching a doorknob may sometimes be accompanied by a zap of static electricity. Occurrences such as this show that the atmosphere is full of electricity. These light- and sound-producing occurrences are called "atmospheric electrical phenomena." Lightning, auroras, and Saint Elmo's Fire are some examples. It is thought that will-o'-the-wisps and other strange events might also be related to atmospheric electrical phenomena. There are even living creatures that emit light, such as fireflies. Light in nature is also a full of mysteries.