Genomic DNA methylation is not stable during development and aging. Recent works, mainly focused in blood, show that DNA hypermethylation in aging preferentially occurs at sequences associated with bivalent chromatin domains in embryonic stem cells that are also frequently hypermethylated in cancer. In my talk, I will comment recent work of our laboratory in which we compare the genome wide DNA methylation status of adult stem cells obtained from healthy individuals of different ages. Using this approach we identified a set of genes showing specific DNA methylation changes in aged stem cells. In addition, by crossing these genes with previously published genome-wide data on chromatin modifications, we identified a global epigenetic signature of aging.