Sodium butyrate is a compound with formula CH3CH2CH2COO−Na+. It is the sodium salt of butyric acid. It has various effects on cultured mammalian cells including inhibition of proliferation, induction of differentiation and induction or repression of gene expression. As such, it can be used in lab to bring about any of these effects. Specifically, butyrate treatment of cells results in histone hyperacetylation, and butyrate itself inhibits class I histone deacetylase (HDAC) activity, specifically HDAC1, HDAC2, HDAC3, and butyrate can be used in determining histone deacetylene in chromatin structure and function. Inhibition of HDAC activity is estimated to affect the expression of only 2% of mammalian genes.