Electronic instruments that mimic the human senses, known as electronic noses and tongues, recently have been developed and used to evaluate the quality of coffee, to assess the odor emanating from packaging materials, and to diagnose diseases such as urinary tract infections. These devices use a common feature—a set (array) of sensors, ranging from a few to 32 or more components. The sensors are nondiscriminating gas detectors of various types, including polymer-based films, electrochemical probes, and thin films. Some use changes in electrical resistance as the signal produced in the sensing process, others produce a color change, while others operate by changing their resonating frequency. In general, these devices do not recognize a specific substance; instead, they detect a signature, a “fingerprint” of an odor, or a quality of what is being measured. The availability of pattern-recognition techniques for effective signal analysis has enabled the development of complex sensor arrays for artificial olfaction.