DNA and Histone proteins are targets for epigenetic modifications. While DNA is only methylated, histones can be targets for diverse modifications such as methylation, acetylation, ubiquitination, phosphorylation and some more. One of the roles of Epigenetics is to drive cellular differentiation from totipotent Stem cells to fully differentiated cell types. This is made by regulating gene expression through modification patterns that differ according to cell types and cellular status. This means that these patterns may significantly differ between stem cells, germ cells, and differentiated cells.