The 3-D image is actually several cross-sections of different brains, each made up from slices of mice brains from a similar demographic (age, gender, etc.) and overlaid to let a viewer zoom in on a specific point and follow individual neuropathways. Each slice is made up of 500 images, but each image contains close to a billion pixels, meaning the project is going for the kind of resolution the complexity of a vertebrate's complete brain requires. It's part of the Mouse Brain Architecture Project, and what's especially surprising is that this kind of resolution is actually a nice middle-ground; MRIs don't provide as much detail, but with electron microscopy you can't do much better than the complexity of a fruit fly's brain. And even at this level, there's a lot of data to handle: this couldn't have been done a decade ago with data storage prices.