The term vomeronasal organ (VNO) refers to a tiny structure identified by topology and histology in the olfactory epithelium (OLE) of some but not all mammals with a highly developed olfactory system (OSY) ( Moran-1995 ). It is found in the rat, mouse and human ( Moran-1995 ) but not the macaque ( Zhang-2003 Francia-2014 ). In the human, it is Identified by direct visualization of the nasal mucosa at the base of the nasal septum, far from the olfactory epithelium (OLE) and the main olfactory receptor neurons (OrNm), which are located high in the nasal cavity. The VNO is the location of accessory olfactory receptors (ORNa), which detect pheromones, that is, 'social smells', sex- and age-specific odorants that are produced and sensed by members of a species but not by those of other species. While the VNO exists morphologically in the human, it is presumed to have little or no functional significance, because its cells stain histologically for epithelial markers and not for neural markers ( Witt-2002 Hartevelt-2012 ). In rodents, the vomeronasal-terminal nerve complex (vtnc) connects the VNO to the accessory olfactory bulb (OLBa). The vomeronasal nerve (vmn), the centrally projecting component of the vtnc, is not present in the mature human ( Witt-2002 ). The terminal nerve (tmn),, the peripherally projecting component, is, however, found in the human ( Wirsig-Wiechmann-2001 Sonne-2023 ). It secretes the neuromodulator gonatotropic releasing hormone (GnRH) to nasal mucosa of the VNO. For function, see accessory olfactory bulb. Final 21 Dec 2024.