Histone acetylation is a biochemical process where an acetyl group is added to the histone proteins that help package DNA in the cell nucleus. This modification typically occurs on the lysine residues of histones and plays a crucial role in regulating gene expression. When histones are acetylated, the DNA becomes less tightly bound, allowing for easier access by the transcription machinery, which can lead to increased gene activity. The process is facilitated by enzymes known as histone acetyltransferases (HATs), which add acetyl groups, and is reversed by histone deacetylases (HDACs), which remove them. This dynamic balance between acetylation and deacetylation is essential for proper cellular function and can influence various biological processes, including cell differentiation and response to stress.