Bioluminescent creatures can produce light through a chemical reaction. LUCIFERIN and LUCIFERASE are combined in the presence of oxygen, it gives off a no-heat, renewable, and clean light.
4/5 of the world's bioluminescent creatures live underwater where sunlight doesn't reach. Ones that we can see include fireflies and bioluminescent algae. Organisms that feed off of these things can also become bioluminescent.
Here's an example of fireflies lighting up
And here of bioluminescent algae.
Currently, bioluminescent algae is being sold in the form of novelty toys. More often than not, the algae doesn't light up as expected because of how delicate they are. Here's an example of that toy:
Designers have also used the bioluminescent algae to create a self sustaining ecosystem / light source. They seem to have the same effect as the Dino Pet toy.
On a larger scale, scientists are trying to genetically engineer this same light producing reaction in other living organisms. If done in plants successfully, this could be a new, clean way to light the streets at night.
Although the most inspiring examples of bioluminescence (for me) are from movies like Avatar.
I wanted to recreate the light quality from the plants in Avatar, so I put flowers in highlighter fluid to see if they would soak it in and show up under a black light. Only the yellow one works, but it still looks pretty cool. Here's the youtube tutorial for it.
Here are the final results under a black light:
*Wish I could post a video, but it doesn't catch the neon as much as a photo.