 The search for reliable indicators of biological age has been ongoing for over three decades without much success. However, recent advances in molecular biology have increased the variety of potential candidate biomarkers that may be considered as biological age predictors. In this review, six potential types of biological age predictors are summarized, epigenetic clocks, telomere length, transcriptomic predictors, proteomic predictors, metabolomics-based predictors, and composite biomarker predictors. Promising developments consider multiple combinations of these various types of predictors, which may shed light on the aging process and provide further understanding of what contributes to healthy aging. The most promising new biological age predictor is the epigenetic clock, but its true value as a biomarker of aging requires longitudinal confirmation. This article was authored by Julia Jilhova, Nancy L. Peterson, and Sarah Haag.