In eukaryotes, there is a set of positively charged, basic proteins called histones. Histones are organised to form a unit of 8 molecules called histone octomer. The negatively charged DNA is wrapped around positively charged histone octomer to form a structure called nucleosome. A typical nucleosome contains 200 bp of DNA helix. Nucleosome constitute the repeating unit of a structure in nuclear called Chromatin.