system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does leftover food that has been in the fridge smell different than when it was just cooked?

And then when you reheat it in the microwave, the smell returns. I’m probably just thinking about it weirdly but if there is a scientific explanation, I would be pleased to know!
gpt
Not too complex. Smells come from particles evaporating up from the object. Cold objects evaporate much more slowly -- and *some* molecules are more affected by this than others, so the blend changes.