The identification of clinically significant protein biomarkers of phenotype and biological function is an expanding area of research which will extend diagnostic capabilities. Biomarkers for a number of diseases have recently emerged, including prostate specific antigen (PSA) for prostate cancer and C-reactive protein (CRP) for heart disease. The epigenetic clock which measures the age of cells/tissues/organs based on DNA methylation levels is arguably the most accurate genomic biomarker. Using biomarkers from easily assessable biofluids (e.g. blood and urine) is beneficial in evaluating the state of harder-to-reach tissues and organs. Biofluids are more readily accessible, unlike more invasive or unfeasible techniques (such as tissue biopsy).