The next ice age: cryo-electron tomography of intact cells.

Recent advances in electron tomography are beginning to reveal the internal structure of eukaryotic cells in their native states in three dimensions at molecular resolution. These observations represent the culmination of years of effort to develop protocols for automated data collection, image reconstruction and cryogenic preservation. Cryo-tomograms of Dictyostelium cells depict distinct populations of ribosomes, proteasomes and networks of actin filaments interconnected by branching or bundling, apparently controlled by strategically placed actin-associated proteins.