If you're anything like me, you'll sometimes wake up wondering why your breath smells like you've eaten three-day-old doner kebab in the middle of the night.
But it's not necessarily something you did (or didn't) eat that causes your breath to pong after having a good night's sleep.
Many people will also wake up with dry mouth, and that's because when you sleep, your mouth provides less saliva.
It's when your mouth is dry that bacteria then thrive and goes on to eat dead cells and food particles on your tongue and around your mouth.
But that's not even the grossest part...
The bacteria then leaves waste on your tongue which has sulphur in it, causing your mouth (and therefore your breath) to smell.
Horrified? Me too.
As to what we can do to help prevent such grossness, there's a few things.
One suggestion is using a tongue scraper - which isn't quite as torturous as it sounds.
It may help remove the nastiness form the back of your tongue.
While they help a bit, periodontist Dr. Wayne Aldridge points out that you'd need to get the scraper quite far back for it to be particularly effective, therefore using a safe-swallow-substance might be better.
An example would be Listerine's Ready! Tabs, which dissolve into a liquid upon chewing that is safe to swallow.
They also stimulate saliva, says Patrica Golas, Ph.D., Principal Scientist and R&D Lead, Oral Care Research, Johnson & Johnson, so can help with dry mouth too.
"They're designed to stimulate saliva, reduce the activity of the bacteria that cause bad breath and neutralise - not just disguise - odour," she explained.
Another thing that can contribute to smelly breath is plaque build up on your teeth.
In a bid to keep plaque at bay, it's said that brushing is 'key' as it 'physically removes bacteria'.
It's also advised that you just generally keep good oral health.
As well as this, as I'm sure you'd expect, food can play a part in bad morning breath - onions and garlic in particular.
Dr. Aldridge said: "Vegetables that are members of the Allium family - like garlic and onions - contain high concentrations of stinky sulphur compounds."
Leeks, shallots, and scallions are also part of the Allium family.
Basically, if you've got a hot date that you're also hoping to see in the morning (if you catch my gist), stay clear of the garlic bread.