A biosensor is an analytical device, used for the detection of a chemical substance, that combines a biological component with a physicochemical detector. Biosensors are devices used to detect the presence or concentration of a biological analyte, such as a biomolecule, a biological structure or a microorganism. Biosensors consist of three parts: a component that recognizes the analyte and produces a signal, a signal transducer, and a reader device. Biosensors are devices comprising a biological element and a physiochemical detector that are used to detect analytes. These instruments have a wide range of applications ranging from clinical through to environmental and agricultural. The devices are also used in the food industry. A commonly cited definition of a biosensor is: “A chemical sensing device in which a biologically derived recognition is coupled to a transducer, to allow the quantitative development of some complex biochemical parameter.” Parts of a biosensor. Every biosensor comprises: A biological component that acts as the sensor.