Epigenome-wide association studies (EWAS) can be used to investigate links between early life environment, epigenetics and disease. However, such studies raise the question of which came first: the mark or the malady? A recent study has demonstrated that EWAS can be performed on neonatal 'Guthrie' heel-prick blood spots. As Guthrie cards are collected from all newborn infants and stored indefinitely in many countries, they represent an important timepoint to compare with later disease-associated epigenetic marks.