Scientists have known for decades about an organ just inside the nasal cavity called the vomeronasal organ or VNO, and its sole function is to detect trace amounts of airborne chemicals called pheromones.

Researchers studying human pheromone response have focused on this tiny organ composed of two small pits a few centimeters inside the nasal passage. Specialized nerve pathways now known as "Nerve O" lead from the VNO and run directly to the limbic region of the brain, bypassing the olfactory cortex.

These nerves were thought to remain dormant the majority of the time, but have now been confirmed to become active with a flood of measurable electrical impulses when subjected to specific human pheromones.

Pheromones detected by the VNO have been shown in laboratory tests to send powerful signals directly to the limbic region of the brain, also known as the “seat of emotions”. This region of the brain is not directly connected to reason or cognitive thought patterns, rather it controls our emotions and sexual desires. So, the stimulating feelings we experience from pheromones can be quite powerful.

When these sexual and romantic feelings overwhelm us, our brains release a chemical called phenethylamine which in turn kicks on dopamine production and the next thing we know, the fireworks begin. This powerful cascade of events can happen in a matter of seconds, but the effects can last a life time. This is the phenomena commonly known as "love at first sight", and is well documented in the annuls of brain literature.