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Your whole nose is lined with mucous membranes ... and in the upper part of the nose, there's this very specialized mucous membrane, and that's where you sense smells. And this is really a unique kind of tissue in the body, first of all, it's the only place in the body where a neuron that's coming from the brain directly contacts the outside world … and the part that sticks out in the environment can is what actually can detect an [odor molecule]. … And then and then it sends a signal like straight to the brain.