Epigenetics is the inheritance of a change in phenotype, or gene expression, that has nothing to do with a change in the underlying DNA sequence of the organism. Epigenetic inheritance is the result of various molecular interactions with DNA, such as methylation of cytosine residues or acetylation of the histone proteins around which DNA is associated. Methylation silences transcription while histone acetylation enhances transcription and both of these changes are heritable, meaning that patterns of gene transcription can be passed from one generation of cells to the next. This is especially important in cellular differentiation during morphological development: for instance, heritable changes in methylation ensure that gene expression in specialised cells remains stable when those cells divide.