 Already in 1958 David Nanney suggested that the difference between genetic and what we would now call cellular epigenetic inheritance lies not in their physical location (i.e., whether they lie in the nucleus or the cytoplasm), but rather that the genetic system maintains a set of “library specifications” while the epigenetic control system (to use his terminology) determines which specificities are expressed in each particular cell, accounting for cell differentiation (Nanney 1958). Thus, according to Nanney, the epigenetic inheritance system plays a regulatory role in relation to the genetic system.