In a live demonstration on Friday evening, Elon Musk’s brain-machine interface company, Neuralink, displayed three pigs that had the new technology successfully implemented in their brains for months. Musk said that he hopes to move to experimenting on humans by the end of the year. The Tesla and SpaceX CEO said that the devices would be surgically implemented into the brain by robots and take data from it to treat brain injuries and trauma—and someday enable symbiosis between humans and artificial intelligence. He described it as a “Fitbit in your skull” during the demonstration.

The Neuralink so far has reportedly been tested by robots on at least 19 different animals and is said to have around an 87 percent success rate. Although Musk said that he wants to implant his first human by the end of the year, scientists told CNBC that there are ethical and safety concerns.