What if we could see through skin? Scientists have managed to do just that, by mixing a common yellow dye with water and applying it on living mice. They used the technique to peer through the skin on mouse skulls and abdomens, according to a report in Science.

The technique has potentially profound implications for medical imaging because it could provide less costly and more effective ways for doctors to see what’s going on in human tissue. The technique, while promising, has not yet been approved in humans.

Scientists Create See-Through Skin in Mice

While the effects of the water and dye combination look like a magic trick, some pretty basic physics explains how it works, says Zihao Ou, assistant professor of physics at the University of Texas and the lead author of the study. It involves different substances’ abilities to either scatter or absorb light.

Living skin scatters light, similarly to the way fog does. Meanwhile, yellow dye absorbs it. Individually, each blocks light from getting through — but by different mechanisms.

However, when you put the two together, the properties change. Dissolving the light-absorbing dye molecules in water changes how the substance bends light. This changes the way molecules that make up skin interact with light. The result of this combination? The dye molecules reduce the amount light scatters in the skin tissue. The end result is akin to clearing fog.

Read More: Why Scientists Created See-through, Shrunken, Glow-in-the-dark Mice

The Physics Behind Transparent Skin Technology

This solution to a practical medical problem started with theoretical physics roots. Ou was studying how microparticles scatter light when they are in an environment that absorbs it.

“During my preliminary experimental test, we noticed that the scattering is different when medium changes from absorbing to non-absorbing,” says Ou. “That motivates us to think absorbing molecules could be potentially used for reducing the optical scattering inside the biological tissues.”

As for the potential application, Ou credits its success to basic scientists working with more applied ones. Besides Ou’s physics background, the research team includes engineering and material science expertise, as well as biomedical knowledge.

Read More: The Funky Physics of Turning an Animal Transparent

Can Scientists Make Human Skin Transparent?

There are some fundamental challenges to applying this technique to humans. Human skin is about 10 times thicker than mouse skin. But Ou says the principles that make it work on mice should — with some tweaking — make it effective in humans as well.

“It does require more efficient and accurate drug delivery strategy and recipe design to achieve an optimal imaging condition with minimum adverse effects,” Ou says.

A team is now experimenting with different ratios of dye to water, as well as with other substances beyond the yellow dye. If the scientists can successfully apply the approach to humans, that could mean less reliance on expensive imaging techniques like ultrasound and MRI.

Read More: 20 Things You Didn’t Know About… Skin

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Before joining Discover Magazine, Paul spent over 20 years as a science journalist, specializing in U.S. life science policy and global scientific career issues. He began his career in newspapers, but switched to scientific magazines. His work has appeared in publications including Science News, Science, Nature, and Scientific American.