Bioluminescence is sort of like the night mode of the natural world. It involves chemical reactions generating light in living creatures. Here is a Ctenophore:

The header is Panellus stipticus fungus.

While the firefly may be the quintessential bioluminescent life form from a human perspective, some marine life makes especially striking use of the technique. There is of course the deep sea superstar anglerfish, yet somehow even stranger is the picture painted by my favorite passage from the Wikipedia article on the topic:

However, some loose-jawed fish emit red and infrared light

Have a glowy good night or day 🛋️🐠