Nucleosome clutch (blue), illustration. Eukaryotic nucleosomes, each consisting of eight histones (green), help structure chromosomes by compacting DNA (deoxyribonucleic acid). Chromatin compaction follows a hierarchical model where nucleosomes form a beads-on-a-string structure. It is indicated that nucleosomes are grouped in discrete domains along the chromatin fibre, which are termed nucleosome 'clutches'. These clutches are interspersed with nucleosome-depleted regions. Differentiated cells contain larger and denser clutches than stem cells. Therefore, nucleosome clutches regulate the accessibility of DNA for transcriptional purposes.