This unit's main objective is to familiarize students with molecular biomarkers and the principles of their identification and detection in molecular diagnosis. A biomarker is a characteristic that can be measured or evaluated as an indicator of a physiological as well as pathological process or response to a therapeutic intervention. Molecular biomarkers are the focus of the development of molecular medicine with molecular diagnostics involved in discovering new biomarkers and defining their role in disease mechanisms. This subject will explain the molecular-based principles used in molecular diagnosis, from the origin of the biomarker used in a given pathology, to the diagnostic method, principle of the method and critical interpretation of diagnostic test results.