Chromatin is the term commonly applied to nucleic acids (especially DNA) and proteins found in the eukaryotic nucleus; its percentage of nucleic acid is about 40%. Chromatin was discovered by Walther Flemming in the 1880s, who noticed that the dense nucleic substance greatly absorbed certain dyes (hence the name "chromatin," which derives from the Greek root "chroma" meaning "color").

Before and during cell division, chromatin gathers into relatively large structures called chromosomes through a complex process illustrated in the figure below. First, DNA wraps around proteins called histones to form structures called nucleosomes; the nucleosomes are then connected by thin strands of DNA, so that the nucleosomes appear as "beads on a string." The strand of nucleosomes continue to coil and pack themselves into successively more complex forms anchored by more proteins, until finally the classic X-shaped chromosomes appear during metaphase.


Chromatin can be divided into heterochromatin and euchromatin. The former material remains condensed