Biomarkers is a word derived from “biological marker,” which indicates a substance or physical event that can be measured and correlated with health, disease or drug treatment. One practical example of a macroscopic biomarker for cardiovascular disease is the measurement of blood pressure. At the molecular level, the expression of certain genes is used as biomarker to determine the appropriate therapy for cancer patients. Biomarkers are thus a key component of Personalized Healthcare approaches. Appropriate biomarkers are also essential to design clinical studies and to define their intended or expected outcome. Diagnostic methods aim at identifying and quantifying disease-relevant biomarkers.