Biomarkers are biological molecules or changes in the body that can be measured and indicate the presence of a particular disease or condition. They are used in research to identify and monitor the progress of diseases, as well as in clinical practice to diagnose and guide treatment decisions. Biomarkers can be found in various forms, such as proteins, genes, hormones, metabolites, and even imaging techniques like MRI scans. They play a crucial role in personalized medicine, allowing for more precise and targeted treatments for patients based on their individual characteristics.