For the first ever time miniature human brains have grown in a new species and scientists have suggested the breakthrough could help with stem cell research.

Scientists created the pin-sized human brains from stem cells and then placed them inside the skulls of mice, where a piece of tissue had been removed to make room for the new organ.

Of the test mice, roughly 80 percent survived the operation, and within two weeks the rodents’ implants had been successfully received and were even spawning new neurons.

The brain implants survived for an average of 233 days, but began the process of dying much earlier.