Smells are one of the most potent ways for a memory to be implanted in our brains, I think.
I remember coming home from college one summer, intending to break up with my girlfriend. But when I went to her house and she came outside to hug me, I smelled the aroma from the flowers in her parents garden, which I associated with first dating this woman the summer before. All the feelings from the previous summer came back to me.
It took me months before I finally did break up with her!