The Field Museum's new "Creatures of Light" exhibit is all about those creatures that arrive in this world "batteries not included," but still light up their surroundings. It's something called bioluminescence.
"It's about living things that create their own light," said the museum's Janet Hong. "From fireflies that you cupped in your hand as a kid, to mushrooms that grow in forests for some reason and no one knows why, to strange fish and squid and creatures in the darkest depths of the ocean where sunlight never penetrates."
There are thousands of different species that can turn themselves on and off with a flick of their switch. They just mix a couple chemicals with oxygen, and presto -- let there be light.
"Animals produce light a lot of times for camouflage to hide from other predators," said assistant curator of exhibits Leo Smith. "They will produce it to find or trap a mate or they will use it find and trap a predator."
We never see the vast majority of these Energizer species. They're in the deepest oceans.
But the firefly? That's a different story. We have seen them, trapped them, touched them.
"The fireflies are out in a forest here in Chicagoland, they're signaling just so the males and females can find each other," said Smith. "It's a love light."
The show is just a field trip away.