If you look closely, you’ll see that mouths are much like fingerprints in how different they are from one another. On the surface, mouths look the same, but the difference is in the details.

Mouths convey emotions—a smile, a frown, a gasp, bewilderment or the inner happiness you can’t hide. That’s not even taking into consideration that lips come in tons of shapes and sizes. It’s no wonder your mouth is a messenger in many ways.

QUIZ: How Happy Are You?

Plastic surgeons have looked over thousands of pictures of beautiful women and men to discover the perfectly proportioned mouth. This is what they found…

• The width of the mouth should be about 1.6 times the width of the bottom of the nose (aka the golden ratio—what a coincidence!).

• If you drop lines down from the inner part of the iris (the colored part of your eyes), your mouth should fit between those lines.

• Your upper incisor (front) teeth should be visible below your upper lip for one to four millimeters and your lower teeth should not be visible when your lips are open. As you get older, your upper lips drop and you see less of your upper teeth. At the same time, your lower lip sags, exposing more of your lower teeth. Shakespeare’s reference to older people as “long in the tooth” describes this drop. The real reason is periodontal disease, where the gum recedes and the bone follows, creating triangles of space between the teeth. This exposes their roots.

• Your upper teeth should also overlap the lower teeth by one millimeter.

• Your jaw should be level. To find out if it is, take a wide Popsicle stick and bite on it. If your jaw is asymmetrical, the stick will tilt.

We’re not suggesting you move your facial features a smidge here and there. We are suggesting that there are objective standards to beauty. If your mouth’s features don’t measure up to the scientific standards, there are plenty of other ways you can make the most of your mouth. Let’s take a closer look at your mouth anatomy when it comes to ideal beauty standards. Here’s a breakdown of the different parts of your mouth, and what these features reflect when it comes to beauty…

Lips: We all know the main things we use our lips for. There’s a lot more to know about your lips, though. The ideal upper lip should be slightly larger than the lower, with a gentle curve that peaks (called Cupid’s bow).