Elon Musk is preparing for the most consequential launch of his career. But this one isn't rocket science—it's brain surgery. Musk's company Neuralink Corp. is seeking a volunteer for its first clinical trial, meaning it's looking for someone willing to have a chunk of their skull removed by a surgeon so a large robot can insert a series of electrodes and superthin wires into their brain. When the robot finishes, the missing piece of skull will have been replaced with a computer the size of a quarter that's meant to stay there for years. Its job will be to read and analyze the person's brain activity, then relay that information wirelessly to a nearby laptop or tablet.