- It's a hot summer night and you're standing at the beach and you notice that with each crashing wave, the ocean begins to glow with ethereal blue light.

Fish are leaving trails of light behind them, like underwater shooting stars.

It might look magical, but in actuality, it's just your friendly neighborhood dinoflagellates, single celled organisms, which glow when disturbed.

That light you're seeing is called bioluminescence.

Some cultures once believed that these lights were doorways to a mythical realm or the spirits of those who passed away.

Today we know it's actually organisms creating their own light, but how does this actually happen and why would these creatures even do it in the first place?

Hi, I'm Niba.

Today we're shining a light on bioluminescence diving deep into how it works, and even making a light show of our own welcome to Big Ideas a a new show from the team behind Deep Look.

While Deep Look zooms in on one small animal, Big Ideas zooms out answering the big questions about how animals survive.

Bioluminescence can be found all over our planet, from marine plankton to fungi and even deep sea creatures.

According to researchers, three quarters of deep sea animals make their own light.

Like this female angler fish.

In the pitch black depths of the ocean, she dangles a glowing lure inside are bioluminescent bacteria that entice unsuspecting prey before she swallows them whole.

Now bioluminescence isn't as widespread on land as it is underwater, but it does exist.

You'll find it in some species of mushrooms and the mycelia or root structure of certain fungi.

And of course, one of the most famous glowing creatures is the beloved firefly, also known as lightning bugs.

But they're actually neither flies nor bugs.

They're actually beetles.

And out of about 400,000 beetle species, only half of 1% of them can actually glow.

So yes, you are special little firefly, and so are all of you other 2000 beetle species in the lampyridae family.

Anyways, while most glowing beetles thrive in tropical humidity, fireflies are very adaptable.

These remarkable insects have spread to every continent except Antarctica.

I guess even fireflies draw the line somewhere.

So what exactly makes these beetles, not flies or bugs, flash when the sun goes down?

What's actually going on when they emit light?

Basically, bioluminescence is light produced inside an organism through a chemical reaction.

These insects produce light in a special organ in their abdomen called a photophore.

We sometimes refer to it as a lantern for obvious reasons.

Scientists discovered that for these beetles to create their special glow, four chemicals need to work together.

There's oxygen, an enzyme called luciferase, the light producing compound luciferin and the energy molecule, a ATP or adenosine triphosphate.

So when the beetles want to light up, they redirect oxygen into their lantern through structures called peroxisomes.

That's where you find the enzyme luciferase.

Luciferase has these pockets or cubby holes that hold the light producing compound luciferin right next to the energy currency of ATP.

And now the stage is set for the bug, I mean insect, I mean beetle's light show.

So when the oxygen gets introduced, it excites the luciferin and the ATP causing the duo to release a burst of energy, which is how these tiny little insects make that big yellow-greenish glow.

We don't have any fireflies in our studio, but we can create a similar chemical reaction using some different substances.

We have luminol, sodium hydroxide, bleach, and the MVP ingredient: oxygen.

This'll create a chemiluminescent reaction that's similar to what's going on in the firefly.

Safety first, though.

Okay, let's see what happens when I introduce the luminol solution to the bleach.

What?

Yo, that was so cool!

The chemical reactions taking place in bioluminescence and in fire are quite similar.

Both are chemical reactions that involve oxygen to create light, but there's a key difference here.

While this one creates light and heat, this reaction only creates light, and that's why this one is called hot light.

And the light emitted by the glowing beetles is called cold light.

The chemical reaction to produce bioluminescence is amazing because it turns all its energy into that iconic glow rather than releasing some of it as warmth.

I mean, imagine if this beloved glowing beetle emitted hot light inside its lantern, I don't think it would survive that experience.

This is a really cool evolutionary marvel, producing light without any heat?

It must serve some kind of purpose.

Some species of glowing beetle start using light as a warning before they're even born.

while they're still in their eggs, and even when they become larvae, they light up to tell predators like frogs or toads, "Hey, don't eat me."

"I taste awful, and might even be toxic."

But as adults, these glowing beetles use their flashing lanterns for the ultimate goal: to attract a mate.

Like nature's version of dating apps.

The guys are the flashy ones flying around, showing off their light patterns like, Hey, ladies, check me out.

Meanwhile, the females are just chilling in the grass or on plants.

But when a female sees a male who's flashing pattern catches her eye, she will flash back.

And that's her way of saying she's interested and wants to chill.

But it's not all romantic fairytales.

In the beetle world, some sneaky female fireflies, also called femme fatals in the Photuris species, are the queens of catfishing.

They copied the flash patterns of females from other species to trick unsuspecting males into thinking they're interested in hooking up.

But when the poor guy flies down excited to meet his match, surprise!

He becomes dinner instead.

Now, these glowing beetles have been around since the age of dinosaurs.

Like the oldest known fossilized firefly is about 99 million years old.

And though it took generations of curious scientists to figure out exactly how fireflies create their glow, today researchers are putting this knowledge to work in some pretty mind blowing ways.

It's even being used in cancer research.

Scientists are taking genetically modified cancer cells that glow and injecting mice with it in order to study cancer more closely.

With the help of specialized cameras that detect this light, they can measure tumor growth or track it spread, which allows them to understand how cancer progresses and also responds to cancer treatment.

So bioluminescence is way more than just a fun light show.

It's a survival tactic, a mating call, and maybe one day a key part of how new discoveries are made.

It's pretty amazing that these little glowing beetles are helping us understand the world we live in.