Chromatin is the physical representation of epigenetics. The degree of chromatin compaction is inversely correlated with gene expression. The epigenome responds to intra- and extra-cellular signals via changes in DNA methylation and histone modifications. Accordingly, the epigenetic landscape visualizes epigenomic changes during cellular differentiation, tumorigenesis and other cellular perturbations. Thus, the proper action of the epigenome has a major impact on our health and disease.