Epigenetics is today one of the main subjects studied in medical genetics. Monozygotic twins are used to prove that differences in the epigenome due to certain factors are the reason why monozygotic twins change as they age. Genes provide the instructions for the development and maintenance of the body. There is a second set of instructions called the epigenome, which interacts with DNA to suppress or activate the expression of certain genes. Epigenetic tags turn genes on or off, without changing the genetic code. In monozygotic twins, the embryo contains the same genome and the same epigenome. Throughout the first years of their lives, twins have a very similar epigenome because they share the same environment. As they age, their environments differ and their genomes remain the same, but their epigenome acts to silence or activate certain genes. Factors such as diet, differences in physical activity, stress and exposure to certain toxins can also influence the epigenome. So, as monozygotic twins age, their epigenomes and gene expressions end up being very different, leading to two very different individuals. Introduction: Conrad H Waddington discovered the term epigenetics to describe the roles of genes in development and to solidify the fact that genes play a huge role. and the development of control. It was therefore in the 1940s that the term epigenetics was invented (Hallgrímsson & Hall, 2011; Morange, 2013). Epigenetics is known to describe the interaction between genetics and the environment around us, describing the types of phenotypes during development. Currently, epigenetics is more specifically concerned with cellular changes that may be heritable, but are not related to DNA sequence changes and can be altered by the environment and the distinct lifestyle of individuals. one can directly interact with the genome to influence epigenetic change. These changes that we observe can be reflected at different stages of a person's life. With the growing knowledge we have today, epigenetics is better understood. New approaches can be imagined to be able to treat and diagnose certain human diseases. Although at present it is unclear whether monozygotic twins are exactly epigenetically identical at birth, further research needs to be conducted in order to gain more knowledge (Czyz et al., 2012) . Monozygotic twins help create a clear understanding of the epigenetic process; this could benefit us in the future. In the future, the concept of epigenetics could help us find treatments for certain diseases, mainly in older people, because epigenetics is known to change with age (Deepti, 2014).