Most babies born in developed countries share a common painful experience — a heel prick that is done soon after birth. Blood from this is deposited onto a slip of paper, called a Guthrie card, which doctors use to screen for devastating and sometimes fatal diseases. A study published today in Genome Research suggests that these cards, which are sometimes stored for decades, could provide an early snapshot of an individual’s epigenome, the chemical changes that influence gene expression and are likely to have a role in heart disease, diabetes, cancer and other diseases.