Cryo-electron microscopy (cryo-EM) instantly cools samples to about −196 °C in liquid ethane, trapping them in a glass-like ice that withstands the electron beam. Because crystals are not required, difficult targets such as membrane proteins and large complexes can be visualised directly. The method has already enabled structure studies of the SARS-CoV-2 spike protein and other drug-relevant molecules.

Traditional X-ray crystallography offers high resolution but fails when molecules refuse to crystallise. Henderson demonstrated that membrane-embedded bacteriorhodopsin could yield atomic data by electron diffraction, proving single particles could carry high-resolution information. Frank created statistical image-processing algorithms that classify, align and average thousands of noisy 2-D projections, while Dubochet established vitrification, turning water into amorphous ice that preserves native structures in the microscope vacuum. Together, these advances allow structures better than 3 Å and reveal solution-state dynamics of large complexes.

Dubochet’s rapid vitrification suppressed nucleation by sub-millisecond cooling across the glass transition, producing homogeneous amorphous ice matrices. Henderson combined low-dose phase-plate imaging of 2-D crystal membrane proteins with electron crystallography diffraction to push resolution from 3.5 Å to 2.8 Å. Frank introduced multivariate statistical analysis using covariance matrices and EM eigen-images for class averaging, and extended common-lines theory to enable ab-initio reconstructions without starting models. With the advent of direct electron detectors and motion-correction algorithms, single-particle analysis (SPA) now reaches ~1.2 Å, ushering in the “resolution revolution” in structural biology.