Proteins and organic molecules comprise complex 3D structures responsible for their functions and properties, and thus it is important to elucidate their structures. Cryogenic electron microscopy (cryo-EM) can be used for various samples under liquid-nitrogen cooling to minimize radiation damage. Single particle cryo-EM can provide high-resolution structures and their atomic coordinates via the image analysis of frozen-hydrated proteins. This method can also be used to study conformational changes in buffer solutions and fluctuations, thereby revealing the structural dynamics. Small crystals of proteins and various molecules yield electron diffraction patterns, and electron 3D crystallography can visualize individual atoms and detailed chemical properties. Cryo-electron tomography is used to examine cell organelles and larger heterogeneous samples.