Conrad Waddington is the scientist who coined the term epigenetics in 1942 as the branch of biology which studies the causal interactions between genes and their products which bring the phenotype (visible features or traits) into being. As this concept overlaps with that of genetics, a better definition may be that proposed by Shelley Berger, Tony Kouzarides, Ramin Shiekhattar, and Ali Shilatifard who in 2009 stated “an epigenetic trait is a stably heritable phenotype resulting from changes in a chromosome without alterations in the DNA sequence“. The Cancer Epigenetics Society’s take is somewhat different and we define epigenetics as “the sum of chromosomal changes that do not involve changes in the DNA sequence and that contribute to a relatively stably heritable phenotype“. The relative stability (or plasticity) of epigenetic inheritance, we think, is of paramount importance both from an evolutionary point of view as well as from a cancer therapeutic perspective.