How does our sense of smell work?

High inside the nasal cavity is a patch of tissue called the olfactory epithelium, containing millions of sensory neurons. Humans have around 400 types of functioning smell receptors, and each odour activates a unique combination of them, letting us distinguish a huge variety of scents. Signals travel directly to the olfactory bulb at the base of the brain and on to regions including the amygdala and hippocampus. This direct connection to emotion and memory centres explains why smells can trigger vivid memories. Smell also creates most of the flavour we experience when eating.