Epigenetics is about regulating gene expression. That is, controlling which of the many genes in the organism's genome actually get "printed out" into actual pr

Epigenetics is about regulating gene expression. That is, controlling which of the many genes in the organism's genome actually get "printed out" into actual proteins in a given situation). Every cell, after all, contains the entire DNA library of the organism, but not every cell needs all of those proteins, and they must not all simply be made into proteins constantly. It's a little bit like preprocessor directives ("if we're on x86, compile this bit; if we're on ARM, compile that bit"). Transcription and translation turns DNA into protein, in my analogy this is the compilation step.