Ed Boyden, an engineer turned neuroscientist, makes tools for brain hackers."Solving the brain" is as difficult as it sounds. A cubic millimetre of brain tissue can house 100,000 neurons, sending signals across a billion connections in mere thousandths of a second. This cross-talk is what turns a lump of spongy tissue into the most sophisticated computer in existence. It is also impenetrable to modern methods. We can zoom out to scan broad regions encompassing millions of cells, or zoom in to dissect the traits of individual ones, but the intermediate world of circuits still eludes us. Boyden likens our current technology to studying one pixel on a computer screen at a time. "Even if you buy a million screens, you won't understand how a computer works by looking at that one pixel," he says. "I'd rather have one computer and look at everything in it." The auto-patcher is one of the tools that Boyden is developing to observe neural circuits in detail, to better understand how the brain computes.