In addition to analysis of the genetic code, in recent years more and more studies have concentrated on changes in the epigenetic code. Epigenetic mechanisms determine which genes in a cell are transcribed and thus form the phenotype of a cell. The epigenetic code can be changed by environmental influences, which allows cells to adapt to longstanding changes in the environment. Therefore, it is feasible to assume that epigenetic changes are the molecular basis for long-term effects of the environment on disease development. In particular in tumors and chronic inflammatory diseases epigenetic changes were found to correlate with disease severity and progression. Knowledge about these epigenetic changes might help that epigenetic modifications can be used in the future as biomarkers, prognostic factors and therapeutic targets.