Histone deacetylases (HDACs) are enzymes that play a crucial role in regulating gene expression by removing acetyl groups from histones, the proteins around which DNA is wrapped. This process leads to a more compact and inactive form of DNA, making it less accessible for transcription. By influencing the structure of chromatin, HDACs can turn genes on or off, impacting various cellular functions. HDACs are involved in several biological processes, including cell cycle regulation, differentiation, and apoptosis. Dysregulation of HDAC activity has been linked to various diseases, including cancer and neurodegenerative disorders, making them important targets for therapeutic interventions.