Chromatin is the material in the nucleus that can be stained with basic dyes during the intercellular phase. The basic chemical component of chromatin is deoxyribonucleoprotein, which is a complex of DNA, histone, non-histone, and a small amount of RNA. It is the form in which the genetic material of interphase cells exists. Direct visualization of higher-order chromatin structure at the molecular scale is of great importance for understanding the impact of chromatin organization on gene expression in many biological processes.