Have you ever seen someone so beautiful  that they look like they’re glowing?

Surely, it must be the result of some  super expensive skincare routine, not because they, I don’t  know, drink enough water. You could never hope to have any  kind of radiance on your budget.

Except...you can. Because right now, you are literally glowing, with a special kind of light  that only stops when you die. And maybe one day, your  doctor could track that glow to make sure you don’t die  sooner than you’d like to. [♪ INTRO] Whether you’re a human or a bacterium, you’re basically a watery bag full  of molecules and chemical reactions.

And because of those reactions,  you’re also full of electrons that are getting excited and relaxing again, which  releases particles of light called photons. Scientists call these biophotons to reflect the fact that they’re made by living organisms. Biophotons are distinct from other  ways life can produce a nice glow.

If you dive into the ocean, you’ll  find bioluminescent bacteria, fish, and other creatures alight  in bluish, greenish colors. That light is also the  result of chemical reactions. But unlike the ones behind biophotons, they depend on a class of  enzymes called luciferase.

We don’t have luciferase in our bodies, so, that’s why you and I aren’t out  here making blue light at night. Meanwhile, literally everything…be  it living, dead, or never alive… is glowing thanks to thermal radiation. That’s because we are currently existing  at a temperature above absolute zero, which means the particles that make us up  are always moving at least a little bit.

For humans, and anything else  around the same temperature as us, that movement mostly produces infrared light. You can’t see it unless you have special  glasses that can capture that light and translate into something visible,  but I promise you that it’s always there. But while death can’t stop your corpse  from emitting invisible infrared light, it can stop you from emitting those  visible-wavelength biophotons.

Exactly how soon after death has been  a bit of a mystery, until recently. And one reason why is revealed  by its alternate name: ultraweak photon emission. Now, technically the human eye  is capable of detecting single, high energy, subatomic particles  that randomly smack into our retinas.

But generally, for our eyes to see  anything, we need a light intensity around one million photons per  square centimeter per second. Ultraweak photon emission is somewhere  on the order of tens to hundreds of photons per square centimeter per second. Which you’ll notice is…less than one million.

But at visible wavelengths, it is  the main way that you’re glowing… assuming you're a non-bioluminescent human. Given a typical 37 degree  Celsius body temperature, your ultraweak photon emission  is over a billion times stronger than your thermal radiation. But biophotons being as dim as  they are doesn’t just make it nearly impossible for the  naked human eye to see them.

It’s also difficult for scientific instruments, which makes it remarkable that  scientists even found them to begin with. Before we can get to that story, though, we have to keep the lights outside  our bodies on, so here’s an ad. This SciShow video is supported  by our Presidents of Science!

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In the 1920s, a Russian scientist  named Alexander Gurwitsch wanted to see if there was a  way for cells to communicate without them touching or being able to  send a chemical signal to each other. His experiment featured two onion roots, separated by either some  quartz or an opaque material. When he saw that the cells in the roots  separated by that see-through quartz divided more, he hypothesized that  they were relying on some kind of electromagnetic radiation…a.k.a.  light…to tell each other to divide.

Since the process of cell  division is called mitosis, he called this signal mitogenic radiation. At the time, it was difficult  for other scientists to observe anything that might support Gurwitsch’s idea. But as the decades progressed, we developed  tools like the photomultiplier tube that could make weak signals  strong enough to detect, and even cameras that could spot single photons.

So we definitely know that biophotons exist, now. But it still takes a bit of effort to study them. For example, according to a paper  published in 2025, the authors couldn’t find any prior research that  investigated death’s effect on ultraweak photon emission…at  least using any imaging technique.

Their study featured four mice…all kept  at the same temperature and in a dark box to prevent both thermal and  visible light pollution. Using cameras that could image single photons, the team took two separate  one-hour-long exposures of each mouse: One immediately before death, and  another half an hour after death. It wasn’t immediately after,  because they had to take the mouse out of the box to euthanize it.

So they had to get everything…including  the body…reacclimated to the darkness. When the researchers looked at the images, they found that biophoton emission  decreased significantly after death. Which makes sense: the  biophotons that living organisms make are the result of normal metabolic functions.

But the team didn’t stop there, because biophotons are also  made when things are abnormal. When we get sick or hurt, or  we’re dealing with some kind of environmental stress like heat or radiation,  our body winds up producing molecules that tell our cells, “Things are looking rough. Someone needs to start doing some damage control.” These signaling molecules are  called reactive oxygen species.

As the name suggests, they have  oxygen, and they’re reactive. And because they’re reactive, you guessed it: they set off the production of more biophotons. This research team studied the influence of extra stress not on mice, but on plant leaves.

Specifically, the species Heptapleurum arboricola. When they cut the leaves of the plant, they found that the plant produced  more biophotons in the injured areas. Now, whether or not plants  are using their biophotons as a type of communication is still unclear.

So Alexander Gurwitsch hasn’t  been completely vindicated, yet. But studies like this do show  us a relatively novel way to visualize the stress that  different organisms go through. Again, this isn’t “stress” like “Oh my  god I’ve got to book it across an airport terminal to avoid missing my connection”, it’s “My body has to fight  off the virus it caught from some rando who wasn’t masking at said airport.” For plants, this could include  tracking infections in wheat, or checking on the quality of organic eggs.

Which both sound incredibly  specific as far as examples go, but that’s because researchers  have actually looked into those. And for humans, maybe one  day scientists will develop a use for biophotons as a noninvasive way to monitor what’s going on in your  skin…and maybe even under it. In recent years, several  research teams have started investigating the effects that different diseases… from arthritis, to diabetes, to cancer… may have on ultraweak photon emission.

It’s still in early days, though. So even though Sephora won’t be selling  biophotons as a glowy highlighter for your complexion, you could say that scientists are still finding them to be…illuminating. [♪ OUTRO]