Smells are first processed by the olfactory bulb, which runs along the bottom of the brain. The olfactory bulb has direct connections to two other brain areas, the amygdala and the hippocampus. These ares have a strong implication in emotion and memory. None of the other senses pass through these two parts of the brain, which makes the sense of smell the most successful for triggering emotion and memory.
Learn additional smell facts in this infographic courtesy of Aromatique.