Electron microscopy and atomic force microscopy studies of chromatin and metaphase chromosome structure

► Review of more than 30 years of TEM and AFM research on higher-order chromatin structure. ► Including cryo-EM, electron tomography, AFM in aqueous media, force spectroscopy and nanotribology. ► Emphasis on the structure of compact chromatin fibers and dense nucleosome aggregates. ► Implications of the discovery of chromatin plates in metaphase chromosomes are discussed. ► A synthetic view of the different chromatin folding possibilities is presented.