You may know that smiling makes you happy (yes, even faking a grin sends happy hormones to your brain) but it's not the only way that the expression you make or the way you move your face might affect your health and happiness.
Here are eight fascinating face facts you should know.
1. Move your eyes if you want to remember something
Left the house and can't remember if you locked the door? Then move your eyes left to right for 30 seconds.
In UK trials, this simple eye movement increased recall by 10 per cent. It works because it helps the right and left parts of the brain work together more effectively, which stimulates recall.
Plus, study author Dr Andrew Parker from Manchester Metropolitan University says the bilateral movement also helps you find the source of the memory.
That's handy for creating what experts call 'true memory' - that is, remembering whether you did lock the door/turn off the gas rather than just thinking you did.
2. Squinting lowers your mood
Summer's here and generally everyone is happier - but if you tend to be in a worse mood when the sun shines, it may have nothing to do with temperature and everything to do with narrowing your eyes to reduce glare!
Squinting uses the same muscles as frowning, and according to Italian researchers this actually triggers a knock-on effect in your emotions that sparks an aggressive mood. It's easy to fix though - a second group in the trial wore sunglasses and that stopped the reaction.
3. Looking cranky reduces anger's harmful effects
Unexpressed anger has been linked to many health problems, including increased risk of heart disease and lung problems, but research from Adelaide's Carnegie Mellon University found that making an angry face when you're annoyed can reduce anger's emotional impact on the body, lowering levels of stress hormones produced and also the effect on the heart.
"And this wasn't extreme anger," says the study's author Professor Jennifer Lerner, now at Harvard University. "It was more akin to feeling indignation in the face of an unfair situation."
Remember that next time someone won't let you change lanes in traffic.
4. Smiling through stress protects your heart
Faking a smile when the pressure is on actually reduces the normal increase in heart rate that occurs during a stressful situation, potentially reducing some of the negative health effects, a US study has found.
"The next time you are stuck in traffic or are experiencing some other type of stress, try to hold your face in a smile for a moment," suggests study author Professor Sarah Pressman from the University of California, Irvine.
"Not only will it help you 'grin and bear it' psychologically, it might actually help your heart health too."
5. Nodding helps build self-confidence
You're about to run 10km, you've trained hard and you think you're going to do a good time. Repeat all of that to yourself at the start line while nodding your head and it could be more likely to happen.
Why? Because according to research at Ohio State University, if you nod while trying to convince yourself of something you're more likely to believe it.
"We often think of nodding as something that communicates to other people but it turns out that it's also communicating to ourselves," says study author Richard Petty.
6. Do you look like you're frowning even when you're not
Then you might be drinking more than you should. In Chinese medicine, lines between the brows are signs that your liver is under pressure, which could be related to overdoing it in terms of alcohol or fatty food.
"However, the area between the brows also reflects issues of emotions 'controlled' by the liver - anger, frustration, irritation and impatience," says Melbourne-based Chinese medicine practitioner Jason Chong.
"The deeper the lines the more significant the issue." The number of lines also counts - two vertical lines, so you look as if you're frowning, is linked to inappropriate expression emotions, so you might be holding things in, or have a short fuse that gets you into trouble.
7. Chewing might stop you worrying
It's more a facial movement than expression but researchers at the UK's University of Reading found that chewing gum is a brilliant way to remove 'earworms' - you know those songs that get stuck in your head and won't go away.
But lead author Dr Phil Beaman suspects that it might also be a good way to turn off negative types of inner speech - like when we worry about nothing or have a poor body image.
Exactly how it works isn't known but chewing does interfere with how we hear sounds in our head.
8. Can't show surprise? You might need a check-up
Not being able to register emotions effectively can be a surprise side effect of heart and lung problems, say US doctors who examined a group of patients in emergency hospital departments who were all suffering chest pain and breathing problems.
The fact the patients weren't able to show surprise was particularly telling - those who couldn't do it were more likely to have a more serious problem with their heart or lungs.
"Being sick creates acute hormonal and neural signals, interpreted by the brain as a combination of fear, disgust and sadness, which converts to a 'sick face'," says Dr Jeff rey Kline from Indiana University in the US. When this sets in, the ability to express other emotions properly is affected.
"Imagine the level of surprise on a person's face at their surprise birthday party - sick people never look like that. The most they can muster is the equivalent of getting something unexpected in the mail." One day Dr Kline hopes the 'surprise test ' might be used to screen people in emergency, helping to determine who might need help fastest.