Chromatin is the fundamental complex of DNA and proteins, primarily histones, that packages the eukaryotic genome into chromosomes within the cell nucleus. As a central academic concept and research field in molecular and cellular biology, it investigates the multi-level structural organization, dynamic states (e.g., euchromatin and heterochromatin), epigenetic modifications (e.g., histone modifications and DNA methylation), and associated factors governing genome function. Research in this area underscores chromatin's critical significance in controlling gene expression, DNA replication, DNA repair, and cell division, processes essential for development, cellular differentiation, and the maintenance of health.