RELION

RELION is software for statistically regularized reconstruction and classification of macromolecular structures from single-particle cryo-electron microscopy images. A particle image is a noisy projection with initially uncertain orientation and displacement. The reconstruction must infer those hidden quantities while estimating the three-dimensional structure. ^[ref]

The Bayesian framework combines an image likelihood with prior information that limits unsupported high-resolution detail. Iterative classification can separate subsets consistent with different structures rather than averaging every particle into one object. Regularization does not guarantee a correct result: starting models, image quality, heterogeneity and validation still matter. A sharp-looking reconstruction is a model inferred from measurements, not a direct three-dimensional photograph.