Cannon led me down into the basement, which he and Sarver have converted into a laboratory. A long work space was covered with Arduino motherboards, soldering irons, and electrodes. Cannon had recently captured a garter snake, which eyed us from inside a plastic jar. “Ever since I was a kid, I’ve been telling people that I want to be a robot,” said Cannon. “These days, that doesn’t seem so impossible anymore.” The pair call themselves grinders — homebrew biohackers obsessed with the idea of human enhancement — who are looking for new ways to put machines into their bodies. They are joined by hundreds of aspiring biohackers who populate the movement’s online forums and a growing number, now several dozen, who have gotten the magnetic implants in real life.