“It’s blatantly obvious when someone points it out, but no one had thought of it for 100 and something years,” said Rowlands, who wasn’t involved in the study but coauthored a commentary published alongside the research.

Along with Jon Gorecki, an experimental optical physicist at the same institution who also wasn’t involved in the study, Rowlands wrote that the approach offered a new way to visualize the structure and activity of deep tissues and organs in a living animal in a safe, temporary and noninvasive manner.

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“It just works. You rub it on a mouse, and you can see what it had for breakfast. It’s that powerful,” he added.

Rowlands and Gorecki said that existing methods to turn tissue transparent use solutions that have side effects such as dehydration and swelling and can alter the structure of the tissue. However, tartrazine was used at a low concentration, and its effects were easily undone, potentially facilitating prolonged study of biological processes in live animals, they wrote.

The FD&C Yellow No. 5 dye, a common food coloring, was used at a low concentration in the study, and its effects were easily undone, according to the researchers.

US NSF

The duo noted the discovery was an example of life imitating art, with the dye solution echoing the serum imagined in “The Invisible Man.”

“The protagonist (in the story) invents a serum that renders the cells in his body transparent by precisely controlling their refractive index to match that of the surrounding medium, air,” they wrote.

“One hundred twenty-seven years later … biocompatible dyes make living tissues transparent by tuning the refractive index of the surrounding medium to match that of the cells.”