Life inside a thin section: tomography.

Introduction Electron microscopic (EM) tomography is proving useful for examining the organization of protein molecules in large molecular machines at critical neural sites, such as synapses. Methods are still in a state of flux, and many steps exist between a neuron and a molecular model of one of its synapses. Here, we show our approach for doing tomography on synaptic structure , hoping thereby to shed light generally on the emerging field of EM tomogra-phy. For a glossary of terms, see Table 1. Much effort had been expended to understand the molecular basis of synaptic transmission and plasticity, primarily by electrophysiology and molecular techniques combined with advanced light mi-the molecular basis of synaptic transmission and plasticity requires understanding exactly how the proteins that make up the synapse are arranged, and this lies just out of reach of current light microscopy. Electron microscopy has the potential to pick the individual trees out of the forest, particularly using the emerging technique of EM tomography. Tissues and cells to be examined by