Cryo EM is a developing protein structure determination method, becoming more widely used as its resolution improves.
Due to the method not requiring a protein crystal, instead only freezing the protein into vitreous ice, the biochemistry is simpler and more reliable. The vitreous ice is formed by freezing the protein in water using liquid helium - because of the rapid temperature change, the water molecules do not have the opportunity to rearrange into an ordered structure, preventing damage to the protein. The proteins are observed by the cryogenic electron microscope in random orientations, which can be reconstructed to give a 3D molecular model.
This method requires high levels of computing power, delaying the ability to use it in many settings. Recent advances in technology have made the computing technology required more widely available, and encouraged development of the technology.
Cryo EM is more widely used with membrane proteins, due to their inherent instability.