Epigenetics is many things to many people. To some, it is a away to explain the mechanisms by which molecular ‘musicians’ bring the instruments that are our genes to life. To others, it is a away to explain the effect of the environment on the genome. I concur with all of the above but where I believe that epigenetics will be most useful is in helping to diagnose and predict disease. Last year a colleague and I wrote a review about this. We are talking biomarkers – naturally-occurring characteristics by which a disease can be identified or monitored. Biomarkers can reflect past environmental exposures, predict disease onset or course, or determine a patient’s response to therapy. Many people don’t realise it but this is already happening in cancer: diagnostic and predictive biomarkers for cancer based on the epigenetic mark of DNA methylation are being used in the clinic. Each of these clinical biomarkers is the result of multiple studies all showing the same result – ‘replication’ Other diseases are not far behind cancer even though their epigenetic changes are smaller in magnitude and need replication. Notable papers have shown that DNA methylation measured at birth can predict obesity during childhood (and here). Others identified potential early markers of type 1 diabetes and potential predictors of response to weight loss in adulthood. Neurodevelpmental disorders such as autism and schizophrenia are also waiting in the wings. Most importantly, as most chronic diseases originate in the womb and leave a latent imprint on the epigenome, this can act as a ‘ticking time bomb’ that, with the ‘wrong’ environmental measures and genetic predisposition, cause full blown heart, liver or brain disorder. If we can read the epigenetic changes predictive of disease risk in the ‘book of pregnancy’, we can not only understand the mechanisms of chronic disease but we can detect them way before symptoms occur. Thus early detection will mean early intervention and a paradigm shift in healthcare from treatment to prevention. Yes,we have a little further to go, but this is a dream worth chasing. I am banking my career on it.