Non-histones: In addition to histones the chromatin comprise of many different types of non-histone proteins, which are involved in a range of activities, including DNA replication and gene expression. They display more diversity or are not conserved. They may also differ between different tissues of same organism.

Roger Kornberg in 1974 described the basic structural unit of chromatin which is called the nucleosome. The structural organization of nucleosome to chromosome is explained in Table 2.

Table 2: The hierarchies of chromosomal organization