The nucleosome is a molecule that facilitates the storage and duplication of eukaryotic DNA in the nucleus. It consists of 8 specific proteins called histones that the DNA coils around. In the figure below, different histones are assigned different colors, and the coiling DNA is shown in gray.
If it weren't for the nucleosome, most eukaryotic cells would not be able to actually hold the huge amounts of long, stringy DNA in their cells. The storage efficiency achieved by nucleosomes is analogous to the construction of a baseball, in which almost 300 m of yarn are wrapped tightly around a cork core to yield a ball with a diameter of only 230 mm.
Nucleosomes themselves then join together and coil together into larger structures called supercoils, to which more supporting proteins are added to yield a final compact chromosome.