The regulatory elements that control genomic imprinting are marked or imprinted during gametogenesis (i.e. gametic marks) or in the embryonic stem cells soon after fertilization (i.e. somatic marks). We defined the Imprintome" as the complete set of these differentially methylated regulatory (DMR) elements that control the parent-of-origin, monoallelic expression of imprinted genes NOT the repertoire of genes whose expression is controlled by these DMRs (Jirtle 2009; Skaar et al. 2012).