Chromatin is made of nucleic acids, such as DNA or RNA, and proteins. During cell division, chromatin condenses to form chromosomes. Eukaryotic and prokaryotic cells differ in where chromatin is housed. In eukaryotes, it is located in the nucleus and in prokaryotes, it is located in the nucleoid.
Chromatin has several functions, including condensing DNA to allow it to fit into the cell, facilitating the control of expression and strengthening the DNA to allow it to undergo mitosis and meiosis. There are two forms of chromatin, euchromatin and heterochromatin. Euchromatin is less condensed and can be transcribed. Heterochromatin is highly condensed and is usually not transcribed.