Visualizing cells at the nanoscale.

Cryogenic electron tomography (cryo- ET) enables the 3D visualization of biological material at a previously unseeable scale. Carefully controlled cryogenic specimen preparation avoids the artefacts that are notorious to conventional electron microscopy specimen preparation. To date, studies employing cryo- ET have mostly been restricted to isolated macromolecular assemblies, small prokaryotic cells or thin regions of eukaryotic cells owing to the limited penetration depth of electrons through ice-embedded preparations. Recent progress in cryosectioning makes it possible to acquire tomograms from many kinds of vitrified cells and tissues. The systematic and comprehensive interpretation of such tomograms will provide unprecedented insight into the molecular organization of cellular landscapes.