Epigenetics is the study of how certain genes are activated without modification at the DNA sequence level, resulting in genetically similar individuals having different clinical outcomes. As contemporary medicine increasingly aims to personalize the medical approach to a patient's genetic profile, the factors that can affect which genes are expressed also increase in importance and relevance to the clinician. This text from experts will give the clinician in Reproductive Medicine a reliable grounding in current thinking and research on this fast-moving topic, with many clinical implications.