Cryo-Electron Microscopy (Cryo-EM) can present samples in a native state with imaging the sample’s intrinsic electron density, providing direct visualization of biological macromolecules, such as protein, nucleic acid, large complexes and so on. Conversely, X-ray crystallography must require crystallization of the specimen within non-physiological environments. The resolution of Cryo-EM maps has been improved up to near-atomic resolution level. Thus Cryo-EM is gaining popularity in structural biology.
Cryo-Electron Tomography (Cryo-ET), one of the techniques of Cryo-EM, is used to produce three-dimensional (3D) pictures from a series of tilted Cryo-EM images. Cryo-ET has gained more and more attention in the field of Cryo-EM in the recent years, which can be applied to study the internal organisms, typically for many structures inside cells, for example, subcellular organelles. Organelle is a specialized subunit within a cell, which contains cytoskeleton, mitochondria, endoplasmic reticulum, flagellum and so on. Cryo-EM allows to study the high-resolution structures of macromolecules, and Cryo-ET provides the information about cellular processes. With the combination of 3D imaging and specimen preparation that preserves the integrity of the cell structure, Cryo-ET can observe the internal structure of cell with high resolution.