The human nose isn't a particularly good one compared to the rest of the animal kingdom, but it's still a complex piece of machinery, with around 450 different types of olfactory receptors.

Each of those receptor types can be activated by a range of different airborne odor molecules, each of which ping multiple different receptors at different strengths. This allows humans to distinguish between more than a trillion different scents, on top of which we can overlay a bunch of taste information to generate the sensation of flavor.

Of course, it's not just how our body senses these things that's amazing – the brain's got the job of taking that huge and constantly changing swarm of electrical sensor data and processing it in real time, cross-referencing each smell signature against an impossibly massive data bank of past experiences so we can recognize it and work out whether to get hungry, or sexually aroused, or simply to wait for the next elevator.