Scientists manage to stimulate eye cells to visualize “olo”, a color never seen before by humans

In a breakthrough that seems straight out of science fiction, a group of scientists has succeeded in getting the human eye to visualize a completely new color, beyond what it can naturally perceive. This color, named olo, is described as a bluish-green with a saturation never seen before. The achievement, published in the journal Science Advances, opens the door to future applications in technology and medicine.

The research team, led by James Fong, Hannah Doyle, and Ren Ng from the University of California at Berkeley, developed a system called “Oz” that stimulates individual cells in the retina, the part of the eye that detects light and color. Normally, the colors we see are the result of the combination of signals from three types of cells called cones (sensitive to red, green, and blue light). However, Oz allows for selective activation of only one of these types of cones, something that does not happen in nature.

Under normal conditions, when we see a green color, for example, not only are the green-sensitive cones (called M cones) activated, but also the red-sensitive ones (L cones) and, to a lesser extent, the blue-sensitive ones (S cones). This limits the range of colors we can perceive. But with Oz, the scientists managed to activate only the M cones, thereby creating a color impossible to see by any other means: olo.

New colour olo — Overview of the principle and prototype system. Credit: J. Fong et al.

The Oz system uses high-precision lasers to send small doses of light to specific cones in the retina while tracking the eye’s natural movements in real time. To do this, the researchers first mapped the retina of the participants, identifying the location and type of each cone. Then, using an advanced eye-tracking system, they aimed the lasers exactly at the M cones, avoiding activation of the other cone types.

Participants in the study described the resulting color as an extremely intense bluish-green, more vibrant than any other color they had ever seen before. To confirm that this color was outside the limits of normal human vision, the scientists conducted comparison tests. When they tried to match olo with traditional colors, participants needed to add white light to reduce its saturation, which demonstrated that the original color was more intense than anything else in the visible spectrum.

This breakthrough could improve display technology, allowing for more vivid and accurate colors. It could also help people with color blindness by enabling selective stimulation of the cones that do not function properly in their eyes.

Furthermore, the Oz system could become a powerful tool for studying how the brain processes visual information. The researchers have already demonstrated that participants can perceive images and videos created with these new colors, suggesting that the brain is capable of interpreting visual signals it has never received before.

Although the current Oz prototype only works in a very small area of the retina (approximately the size of a grain of sand viewed from a meter away), the scientists hope to expand it in the future. This will require technical advances, such as the ability to map and stimulate millions of cones in real time, even as the eye moves freely.

SOURCES

James Fong et al., Novel color via stimulation of individual photoreceptors at population scale. Sci.Adv. 11, eadu1052(2025). DOI:10.1126/sciadv.adu1052