Cells of a multicellular organism are genetically identical but differ in structure and function. This heterogeneity is created by several epigenetic mechanisms during the development of the organism. The epigenetic changes- including DNA methylation, histone post-translational modifications, chromatin remodeling and RNA interference have all been shown to control chromatin structure and regulate a plethora of cellular and organismal processes. There is a strong evidence that epigenetics play a crucial role in the development of diseases such as cancer, schizophrenia or metabolic disorders. The epigenetic regulation underlie memory formation or adaptation to external stimuli. The extent to which environmental effects can provoke epigenetic responses represents an exciting area of future research. Here we review the current knowledge about the epigenetic mechanisms and their relation to the human health and disease.