A mini-brain just grew a pair of mini-eyes... Yes, you read that right...

Neuroscientist Jay Gopalakrishnan of University Hospital Düsseldorf in Germany and his colleagues revealed in a paper published in Cell Stem Cell that they grew optic cups on human-derived brain organoids in a lab. 

The results help in reaching a better understanding of the process of eye differentiation and development, as well as the diseases that affect the eyes.

And why did these brains develop eye-like structures? To perceive light... yes, quite shocking.

"Our work highlights the remarkable ability of brain organoids to generate primitive sensory structures that are light sensitive and harbor cell types similar to those found in the body," said Gopalakrishnan.

Brain organoids aren't true brains, they're not fully developed. They're small structures grown from pluripotent stem cells harvested from adults. Pluripotent stem cells have the potential to grow into different types of tissues. 

These cells are stimulated to grow into brain tissue. They're not capable of complicated things like thought, emotion, or consciousness. These kinds of brains are used to test for drug responses or observe cell development under different conditions. This time, the work was on eye development.

"Eye development is a complex process, and understanding it could allow underpinning the molecular basis of early retinal diseases," the paper said. "Thus, it is crucial to study optic vesicles that are the primordium of the eye whose proximal end is attached to the forebrain, essential for proper eye formation."

The good thing is that these results were also reproducible; of the 314 mini-brains the team grew, 73% developed optic cups. "We believe that [these] are next-generation organoids helping to model retinopathies that emerge from early neurodevelopmental disorders."