A closer look

Freezing living tissue so fast that ice crystals don't have time to form is the only way to see a thought in transit. Using cryo-electron tomography, scientists blast these frozen synapses with electrons to build 3D maps of synaptic vesicles—the tiny cellular bubbles carrying neurotransmitters. It turns out our brain's communication network looks less like a neat wiring diagram and more like a chaotic, crowded subway station frozen in absolute time.