All living things emit a faint glow. Could this light be useful?

In 2025, quantum physicist Daniel Oblak and his colleagues published images of mice that made headlines around the world. The researchers put four anaesthetized mice inside a dark chamber and pointed a sensitive camera at them. It picked up a stream of photons emitted from the animals’ skin: a light signal too faint to be seen by the human eye, but visible in the camera images as a ghostly, mouse-shaped glow 1 .

The mice were killed at the end of the experiment, and almost as an afterthought, the team placed the dead animals back into the chamber to image them again. This time, the glow had disappeared; aside from a few remaining spots of light, the mice had essentially dissolved into background noise. Seeing the images was “a defining moment”, says Oblak, who is based at the University of Calgary in Canada. It was as if the researchers had photographed life itself.

A sensitive camera picks up biophoton emissions from a mouse (alive, left; dead, right). Credit: Lana Frankle/University of Calgary

The study went viral. The researchers were inundated with messages, from a healer’s claim that his hands emitted light, to eyewitness reports of glowing trees; headlines around the world asked whether auras are real. Oblak emphasizes that the photons he captured have little to do with such claims, not least because the naked eye can’t see the faint emissions. He sees it instead as the mark of a long-misunderstood field finally coming of age: the study of the ‘biophotons’ produced by living cells across the tree of life.

That biophotons (also known as ultraweak photon emissions) exist had been established long before Oblak’s team took the striking images. The emissions stem from metabolic processes inside cells, typically in their mitochondria. But he and other researchers are studying them in the hope that they will be useful as subtle markers of disease or health. And if scientists can confirm hints that cells themselves also react to the photons, that could expand their understanding of how life works. “If you can prove that cells communicate by light, it would be fantastic,” says Michal Cifra, a specialist in bioelectrodynamics at the Czech Academy of Sciences in Prague.

“It’s one of those fields that feels like it is on the edge of respectability,” says Nick Lane, who studies mitochondrial biochemistry at University College London. “That doesn’t mean it’s wrong.”

The idea that cells might communicate through extremely low-intensity light was first suggested in the 1920s by Russian biologist Alexander Gurwitsch 2 . He conducted experiments with onion roots, reporting that a growing root tip could trigger cell division in a neighbouring root. The effect was blocked if the roots were separated by opaque or glass plates, but persisted if the plate was made of quartz, which lets through ultraviolet radiation. He concluded that the root cells were producing, and responding to, photons of UV light. A flurry of research followed, says Cifra, but the effect was hard to replicate. “People lost interest and thought it was just pseudoscience.”

In the 1950s, studies with photomultiplier tubes, devices that convert faint light into electric signals and are sensitive enough to count individual photons, confirmed that living systems, from bacteria to plants and mammals, do indeed emit light 3 . Its intensity falls slightly below the limit of dark-adapted conscious human vision, at just tens to hundreds of photons per square centimetre per second, and it covers a range of wavelengths that include visible light, from UV to near-infrared 2 . This phenomenon is distinct from both thermal radiation (which is produced by all surfaces, living or not, as a function of temperature) and the much brighter light produced by bioluminescent organisms, such as fireflies and jellyfish.

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