Native CenH3 core particle complexes are tetrameric under physiological salt concentrations. Hydroxylapatite-bound chromatin was purified from interphase cells to enrich for histone core particle complexes immunoprecipitated using an anti-CenH3 antibody and visualized by atomic force microscopy. The unbound material contains predominantly canonical histone core particles and provided a control. Only particles more than 1.65 nm high and 6 nm in radius in the samples were measured to exclude small non-nucleosomal particles and debris. Heights were measured for an equal number of particles for CenH3 (red) and unbound (green) particles. Sample images are shown as insets, where the bar is 100 nm, and the Z range is shown at the bottom of the images.