Flying and glowing Photinus pyralis, a firefly.

Omphalotus nidiformis

Example of a bioluminescent species of mushroom...

...glowing with the lights off.

Bioluminescence is how living things produce light. Often this is done by symbiosis. The larger organism contains, often in a special organ, microorganisms which make the light. Eukaryote protists have special organelles, and some bacteria also produce light. Bioluminescence is the result of chemical processes, where the energy produced is released as visible light.