What is the vomeronasal organ (VNO)?

The vomeronasal organ (VNO) is a cone-shaped organ in the nasal cavity, and is the body's only receptor of pheromones. The normal receptors in the main olfactory system in the nose do not respond to pheromones, but do respond to normal scents (such as perfume, spices, and other scents, aromas and odors). Conversely, the VNO, which is part of the accessory olfactory system in the nose, does not respond to normal scents, but does detect odorless, barely perceptible pheromones. That's why it's often called our “sixth sense” because it allows us to respond to pheromones that we can neither see, smell, hear or touch.

The VNO not only detects the pheromones, but also releases the mysterious agents of enticement encoded in their chemistry -- thereby causing a host of biological reactions that affect human behavior. Among other things, pheromones have been shown to excite sexual desire and guide people in their choice of sexual partners.