Molecular model of a chromatin fiber. This fiber has a length of 30 nm and would use 20.000 base pairs of DNA. The centre is helically arranged and consists of 100 nucleosomes. Chromatin is a complex of macromolecules found in cells, consisting of DNA, protein and RNA. The primary functions of chromatin is to package DNA into a smaller volume to fit in the cell, to reinforce the DNA macromolecule to allow mitosis, to prevent DNA damage and control gene expression and DNA replication. Chromatin is only found in eukaryotic cells.