Book excerpt: Electrochemical Biosensors summarizes fundamentals and trends in electrochemical biosensing. It introduces readers to the principles of transducing biological information to measurable electrical signals to identify and quantify organic and inorganic substances in samples. The complexity of devices related to biological matrices makes this challenging, but this measurement and analysis are critically valuable in biotechnology and medicine. Electrochemical biosensors combine the sensitivity of electroanalytical methods with the inherent bioselectivity of the biological component. Some of these sensor devices have reached the commercial stage and are routinely used in clinical, environmental, industrial and agricultural applications. - Describes several electrochemical methods used as detection techniques with biosensors - Discusses different modifiers, including nanomaterials, for preparing suitable pathways for immobilizing biomaterials at the sensor - Explains various types of signal monitoring, along with several recognition systems, including antibodies/antigens, DNA-based biosensors, aptamers (protein-based), and more