TAAR (Trace Amine-Associated Receptors) is a class of G protein-coupled receptors (GPCRs), including multiple subtypes such as TAAR1 to TAAR9. They are primarily composed of seven transmembrane domains and are located in the central nervous system and peripheral tissues, especially in olfactory epithelial cells. TAAR receptors perceive trace amine compounds and are involved in biological responses such as olfactory signal transduction, emotion regulation, and neurotransmitter release. Activation of TAAR receptors can trigger multiple signaling pathways, such as the cAMP and MAPK pathways. The expression of TAAR genes is tissue-specific, and their mutations or polymorphisms are associated with various diseases, including psychiatric disorders, metabolic disorders, and cancer.