The measurable indicators of a biological condition or state are termed as biomarkers. They can be evaluated and measured through the soft tissues, urine and blood. Biomarkers can be used to study pathogenic processes, normal biological processes and pharmacological reaction to a therapeutic intervention. Biomarkers are broadly categorized into diagnostic biomarkers, predictive biomarkers and prognostic biomarkers. A diagnostic biomarker is a traceable substance which is introduced into an organism to evaluate organ function as well as other aspects of health. It can also be used to detect a particular disease state. General characteristic changes or complex organ functions in biological structures may also serve as biomarkers. This book traces the progress of the research in the field of biomarkers and highlights some of its key concepts and applications. It will also provide interesting topics for research which interested readers can take up. This book is a resource guide for experts as well as students.