The "Shoop-Shoop Song, (It's in His Kiss)," sung by both Betty Everett and later Cher, says it all.
"Think about all those date-movies where that long-awaited first kiss brings sighs and heart flutters to the audience and seals the deal between the couples on the screen," said Sarasota, Fla., psychologist and licensed clinical social worker LeslieBeth Wish.
"The lips are very sensitive tissue, with many nerve endings that signal reactions such as hot and cold, sharp and soft," she said. "These same nerve endings also activate our feelings of closeness and attachment by arousing the brain's love chemicals such as oxytocin."
On Valentine's Day it is worth noting that the romantic kiss may be underrated in a fast culture that celebrates booty calls, pornography and online dating.
"Despite the casualness of sex these days, kisses still pack a serious punch," said Wish. "Good kissers know not to swallow up the mouth of the other, not to jam their tongue down the partner's throat or knock their teeth. Kisses are such powerful connectors that the moment of the first touch can overwhelm you with pleasure."
From Alfred Eisenstaedt's famous photo of the sailor kissing the nurse after World War II, to the lip-lock of gay cowboys Heath Ledger and Jake Gyllenhaal in the 2005 film "Brokeback Mountain", a relationship can truly be sealed with a kiss.
It can also break the deal.
"The worst kiss is the kind when it feels like a serpent has just entered your mouth and is swirling around inside of it," said Severin Witte, a 22-year-old college senior from Brenham, Texas.
An estimated 59 percent of men and 66 percent of women end a relationship because of a bad first kiss, according to Sheril Kirshenbaum, author of "The Science of Kissing: What Our Lips Are Telling Us."
"So much information is exchanged with a kiss," she said. "One kiss and everything can be completely off. It's the ultimate litmus test."
Research for her recent book revealed that, as a rule, "men prefer open-mouth kissing, and women complain about too much tongue," said Kirshenbaum.
The kiss may even serve an evolutionary purpose. Men's saliva contains a small amount of testosterone that can, over repeated exposure, arouse a woman's libido and eventually persuade her to mate.
In a a study at the State University of New York at Albany, men described kissing as a "means to an end...something else down the line," but women saw it as a route to a deeper relationship, according to Kirshenbaum.
Women are also more sensitive to scent and taste, using their senses to detect if the man is the "right match."
"Kissing is such a good example of a behavior that is both nature and nurture," she said. "We seem to have an instinctive drive to kiss and connect in some way."
Man's earliest kisses were with the nose, kind of like the Eskimo rub, according to Kirshenbaum, probably allowing humans to reconnect with relatives and find out clues about a person's health.
Kissing may have moved to the mouth as humans became sensitized to the color red, finding ripe fruits for food. That may have led to a woman's red lips, an indicator of a potentially fertile mate. Modern studies show that the color red makes the heart beat faster and may be the reason why women still use lipstick.