A biomarker is a measurable indicator of a biological condition or process. It can be a substance produced by the body, such as proteins or hormones, or a change in a biological measurement, like blood pressure or imaging results. Biomarkers are often used in medicine to diagnose diseases, monitor treatment responses, or predict outcomes. In research, biomarkers help scientists understand disease mechanisms and develop new therapies. For example, cancer biomarkers can indicate the presence of tumors or how well a treatment is working. Overall, biomarkers play a crucial role in personalized medicine, tailoring treatments to individual patients based on their specific biological markers.