When the cell cycle is at the phase known as interphase, chromosomes present two types of chromatin under a light microscope: a highly condensed portion, known as heterochromatin, and a less condensed one, termed euchromatin. Euchromatin is the dispersed portion of chromatin that is transcriptionally active during interphase. In other words, euchromatin contains genes capable of transcribing genetic information into proteins that are necessary during interphase for young cells' maturation, metabolic functions, or DNA repair. Chromatin is comprised of DNA filaments and histone proteins, as well as some RNA molecules and constitutes the fibre of which chromosomes are made.

Euchromatin is found in two different states of condensation during interphase: about 10% is in the form of active euchromatin, thus being the less condensed form, while the remaining euchromatin remains in a more condensed state. However, the latter state is still less condensed than heterochromatin, which is also found...