Modulators and inhibitors are used in enzyme inhibition assays to study histone deacetylation, or the removal of an acetyl group on a histone, which impacts the regulation of DNA expression. Histone deacetylation modulators and inhibitors inhibit histone deacetylases (HDACs) also called lysine deacetylases (KDACs). They are crucial to advancing epigenetic research in cell cycle regulation, cell proliferation, and development of cancer.