It will be four years later. You will be walking down a tree-lined street after a day of classes, dappled sunlight shining softly through a layer of swaying branches, all lilting and turning and twisting in the breeze. There’s a good chance you will be deeply content, breathing in a lungful of fall air that has just begun to turn. You may cross paths with a smiling stranger on the sidewalk, nod at her, and as she passes, catch the end trail of her perfume. The same warm perfume that the really cute girl in your sophomore-year science class always wore.

Suddenly, faster than you can imagine, you are fifteen and hopelessly confused by talk of stoichiometry and chemical properties. You can almost feel the harsh school air conditioning, blinking at the artificial lights bearing down on you. The cold metal seat of the lab chair digs into the backs of your knees. And there, just as you remember her, is the laughing girl with deep brown hair who pokes gentle fun at you and smells like plum and jasmine. She looks at you with teasing eyes and makes a joke about the quizzical expression splayed on your face. All you can do is look back and hope your gaze isn’t too adoring.

With a rude shock, you’re back on the pavement in your college town, blinking in confusion and stunned at the sharpness of a memory you didn’t know still existed. You haven’t talked to that girl since the night you staunchly avoided her at the beach bonfire, haven’t thought about her since your best friend mentioned seeing her at your favorite hometown coffee shop. And yet there you were, dragged through space and time to your high school chemistry class by the fleeting scent of the perfume she wore four years ago.

We like to think that our emotions are entirely cerebral, feelings swirling in our minds that are dictated by our immediate thoughts and careful coaching. However, certain smells, sounds, and sensations are inextricably intertwined with the times and people in our lives who brought about these experiences. Whether we may like it or not, our minds are programmed to associate otherwise innocuous sensations with past memories. We can’t predict how the opening chord of a forgotten song makes neurons fire, how rapidly synapses connect at the scent of a once-dear recipe baking in the oven. These associations remind us that sometimes, our bodies remember before our minds do. Try as we might, there is no stopping the chemical reactions that take place inside our brains, sometimes slamming us with the memory of experiences long gone.

It can be scary to think about how involuntary this process is; how we can be overtaken by memories without warning or reprieve. And while it can be gut-wrenching to know that these experiences live within us and can shoot to the surface at any given moment, it is also precious to realize how absolutely we are comprised of the past moments we have lived. There is something incredibly comforting in knowing that these moments will always be within us, housed in synaptic connections that may lie dormant for years, only to pick up instantaneously at the slightest suggestion of recollection. I may be walking down a different tree-lined street in another four years and breathe in a lungful of fall air only to be transported without warning back to my college town, watching the trees sway and walking with a backpack full of notes I will no longer remember.