If you want to study the effects of drugs or transplants on the brain without operating on the real thing, you typically have to break out some microelectronics and build a model yourself. Not exactly convenient or cheap, is it? If Brown University scientists have their way, however, just about any lab could make some simulated brain matter of their own.
They've developed a technique that creates a miniature brain (really, a bundle of electrically active neurons) by extracting cells with a centrifuge and seeding a cell culture. So long as you have two to three weeks and 25 cents' worth of material, you'll have a complex, three-dimensional neural network to tinker with.