Histone modifications are chemical changes to the proteins called histones that help package and organize DNA in the cell nucleus. These modifications can influence how tightly or loosely DNA is wrapped around histones, affecting gene expression. Common types of modifications include methylation, acetylation, and phosphorylation. These modifications play a crucial role in regulating various cellular processes, such as cell differentiation and DNA repair. By adding or removing specific chemical groups, cells can control which genes are turned on or off, allowing for precise responses to environmental signals and developmental cues.