The efforts to build a mind-controlled prosthetic at Johns Hopkins Applied Physics Lab got a lot of attention when Facebook announced the Laurel center’s involvement in a new brain-powered push.

But the robotic arm deserves consideration on its own, and that’s what Quartz provides in a very visual feature on the project.

The arm, known as the Modular Prosthetic Limb, is still in the research phase. The feature describes its use since 2014 by “Johnny,” a Florida man who had his arm amputated as a result of cancer.

Along with providing more freedom of movement than other prosthetics, the arm can be controlled by Johnny’s thoughts as a result of a pair of surgeries that allow it to attach to his skeleton and nerves. For now, he’s the only one with that capability, and is undergoing training to prepare to take it home.

Researchers will track how Johnny responds just as much as how the arm works. When the piece describes him getting “more attached” to the arm, it’s blurring the mental and physical in a way that seems to have just as many unknowns as the limits of the technology.