Using a newly developed method, researchers at the Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA) have been able to shed light on the complexity of genome reorganization occurring during the first hours after fertilization in the single-cell mammalian embryo. Their findings have recently been published in the journal Nature. The team of researchers (from three continents) have discovered that the egg and sperm genomes that co-exist in the single-cell embryo or zygote have a unique structure compared to other interphase cells. Understanding this specialized chromatin “ground state” has the potential to provide insights into the yet mysterious process of epigenetic reprogramming to totipotency, the ability to give rise to all cell types.