My friend texted me something today that she thought I'd find interesting.

She had a meeting for work in an office she'd never entered before. Immediately as she entered the room, conflicting feelings of happiness and awkwardness washed over her.

The smell. It wasn't necessarily good or bad—just distinctive. And it didn't smell like anything in particular. All she knew was that it had an odor exactly like her boyfriend's dorm room when she was a freshman in college—something she hasn't experienced in five years—bringing back the paired feelings of excitement and nervousness that come with new relationships. And those of, well, being in a boy's stinky dorm room.

We've all experienced this at one time or another: a familiar perfume, a family recipe in the oven, the scent of a bonfire—they all bring back a flood of memories, momentarily whisking us away to re-live our past. But why does this happen?

One of animals' most primal senses is that of smell. If you look at a rat brain, the olfactory bulbs (the two little notches at the top) take up a significant portion of the total surface area. In the human brain, the piriform cortex (our primary olfactory cortex) is composed of three primitive layer . . . More