Svoboda, 38, and his Long Island, New York, team needed a microscope powerful enough to image synapses, the spaces between neurons where the cells communicate. Synapses are one billionth the size of a rice grain, so the resolution required was 1,000 times that of an MRI. Svoboda based his design on cutting-edge two-photon laser scanning microscopy. Next he obtained mice engineered to express a green fluorescent protein when their neurons are activated. Finally, he figured out how to implant a tiny piece of glass into a mouse's skull--creating a window onto its brain.