The DNA double helix [blue chain] is wrapped twice around a octamer core unit  [purple spool] that comprises eight histone proteins. These nucleosomes are separated by a run of spacer DNA complexed with a single histone H1 unit.

    At the tertiary level [right], six nucleosomes form a solenoid organized around their H1 histone spacers [white oblongs]. Note [upper left] that each solenoid is connected to the ones in front of and behind it, to form a compact coil.