Epigenetic clocks are important tools in modern aging research. Typically, they use characteristic DNA methylation patterns in the genome to precisely predict a person's age and infer conclusions about the individual's biological aging processes. However, why this works so well and what biological mechanisms are behind it remain unclear. Researchers at the Leibniz Institute on Aging—Fritz Lipmann Institute (FLI) have now investigated the basis of established epigenetic clocks and developed a new model, TFMethyl clock, that combines predictive accuracy with improved biological interpretability.