Chemosensation, a fundamental process shared by most multicellular organisms, is responsible for recognizing external chemical signals that influence behavior. The processing of chemical signals in the environment is essential to detect and to assess the availability and quality of food, reproductive partners, prey and predators. Animals modify their behavior based on a wide variety of environmental cues. The biochemical and physiological processes of chemosensation involve the recognition of small chemical molecules by specialized transduction pathways in the organism. These pathways are responsible for the transformation of information from extrinsic molecules into signals that the nervous system can interpret.