The scientific community knew that scent is closely related to memory, as people can recall events / places with a certain smell when they smell the associated scent easily.
Now, they’ve found out that if you have a task that requires studying, then associate that with a smell and then throw that smell at you during deep sleep, you will have remembered what you studied very much better than if you hadn’t used the smells.
Interestingly this doesn’t work if you replay the smell during REM sleep, as the hippocampus isn’t activated, making researchers think that REM sleep accounts for absorbion of activity and emotive memory.