Face It: What Makes Us Beautiful

Michelle Pfeiffer, who is on the verge of turning 50, dominated the red carpet Monday at the premiere of her new movie "Hairspray" and reminded many that she is still one of the most beautiful women in the business.

To many, Pfeiffer has the quintessential beautiful face. Appearing almost symmetrical, her full lips, high cheek bones and captivating eyes have men swooning and women green with envy.

But what makes someone beautiful and attractive to others is a difficult question to answer. What characteristics, if any, truly define a beautiful face?

Face Value

There are certain characteristics people possess that make them especially beautiful, like eyes, lips and cheekbones, several professional celebrity and fashion photographers told ABC News. But the importance of symmetry, or when all facial features are lined up perfectly with one another, is something that photographers don't all see eye to eye on.

Nigel Parry, a portrait photographer for more than 20 years, has worked for Vogue and W Magazine, among many others. He has photographed the mugs of Penelope Cruz, Angelina Jolie and Meg Ryan. To Parry, beauty is in the imperfection.

"Superficially, what makes a classic pretty face is generally something a little unusual -- there shouldn't be perfection on both sides," said Parry, who has also shot Mary Louise Parker and Gwyneth Paltrow. "The symmetry should always be off."

Particular features that stand out to Parry as especially pretty are uneven eyebrows and big eyes.

"To me, a classic face is Cate Blanchett, she has a fantastic looking face and the thing with her is she emanates all that's wonderful inside as well," said Parry, who also says that Debbie Harry and Michelle Pfeiffer have "the best mouths."

George Zimbel, who photographed Marilyn Monroe and Jackie Kennedy, said that to him, beautiful faces are the ones that jump out at him, and there is no rhyme or reason as to which ones will catch his eye. Personality, he agrees, adds a lot to a person's beauty.

"[Marilyn Monroe] was so 'on' all the time," said Zimbel, who photographed the icon in 1954 in New York and remembers Monroe's beautiful personality the most. "I don't know how the hell she did it, but she never lost it."

Celebrity photographer Patrick McMullen, who has photographed Kate Moss, Nikki Taylor and Elizabeth Hurley, has a favorite in Pfeiffer, who he has also worked with.

"Michelle Pfeiffer, she's just beyond," said McMullen, who also names Julia Roberts and Elizabeth Hurley as favorites."[Pfeiffer] is just so damn beautiful. She does have the intelligence and she's got the classic beautiful looks. She's so stunning and she's rare."

Katie Ford, CEO of Ford Models, has worked with hundreds of models. She still maintains that it's symmetry that makes a face very beautiful and that the first things she looks at when scouting are eyes, lips and nose.

Ford recognizes uniqueness too, though, and said that today, much of what the fashion industry considers beautiful does have some kind of an edge.

"There is no perfect proportion," said Ford.

One photographer, Mark Robert Halper, who has worked with stars like Tori Spelling and Michelle Williams, believes that symmetry is an important contributor to facial beauty.

"Facial symmetry is a big factor in beauty," said Halper. "We perceive symmetrical faces as prettier."

The Science Behind the Beauty

Believe it or not, there is a method to the madness that is beauty, and many scientists have capitalized on figuring out exactly what it is.

According to a complex set of measurements and calculations, some researchers believe there are dimensions that, when followed, will create a perfect face. In fact, some scientists conducted research that showed people with the most symmetrical faces lose their virginity earlier, hinting at the idea that the more symmetrical your face, the more desirable you are.

The complex set of numbers and measurements hardly guide the fashion industry or even the medical profession, experts told ABC News. While these measurements are used as very loose guidelines for plastic surgeons, proportion -- and not precise symmetry -- is really the key to beauty.

"It's really about the proportions of the face, balance and the harmony of the face," said Dr. Sherrell J. Aston, professor of surgery at New York University. "General symmetry is important but not always there. It's not unusual to see one cheek bone a few millimeters flatter than the other."

"Beauty is not a mathematical equation," said Dr. John Canady, professor of plastic surgery at the University of Iowa. "The human body is not a block of marble or a piece of wood. It stretches and it movies and I'd be reluctant to apply a strict mathematical formula to it. It's a combination of an art and a science."

The Beauty Within

While great eyes and good skin are characteristics many photographers agree can't hurt, when asked how they define beauty some said that it is what's on the inside that means the most.

"The qualities of a beautiful face generally tend to come from a beautiful inside," said photographer Parry. "When someone is really gorgeous inside, it shows on the outside."

"It's a face that just very quickly makes a connection with who is looking at that face," said Zimbel, who has been a photographer for more than 60 years and documented many presidents, such as Harry Truman and Richard Nixon.

"Certain people seem to have some soul behind them or some old-fashioned sort of kindness that shows through," said fashion photographer McMullen.

"Some have a hard, bossy way about them that shines through and makes them seem not as attractive. Somehow, people who are happy to see you always look more beautiful," he added.

Ford, whose modeling agency made women like Christy Turlington famous, agrees that beauty really is a matter of a perspective.

"I think that right now more than at almost any other point in time there is a great diversity of looks that people consider beautiful," said Ford.

Beauty, it seems, really does lie in the eye of the beholder.