Losing a tooth can be a scary experience, so it’s no surprise that parents throughout history have created rituals to celebrate this rite of passage. In the United States, children who leave a newly lost tooth under their pillow know to expect a nocturnal visit from the Tooth Fairy, who might leave a shiny quarter, a new toothbrush, or perhaps even a crisp $20 bill! But how did this tradition begin, and what is a tooth really worth? Here are 13 bite-sized facts about our favorite dainty dental dealer.

1. THE TOOTH FAIRY IS YOUNGER THAN YOU MIGHT EXPECT.

Compared to the two other main figures in modern American mythology, the Tooth Fairy is definitely the new kid on the block. Santa Claus can be traced back to Saint Nicholas, born around 280 CE, and the Easter Bunny arrived in the United States with German immigrants during the 1700s, but the very earliest reference to the Tooth Fairy appears in a Chicago Daily Tribune "Household Hints" column from September 1908. Tribune reader Lillian Brown wrote in to suggest that "Many a refractory child will allow a loose tooth to be removed if he knows about the tooth fairy. If he takes his little tooth and puts it under the pillow when he goes to bed the tooth fairy will come in the night and take it away, and in its place will leave some little gift." The story was further popularized by Esther Watkins Arnold’s 1927 play for children, The Tooth Fairy.

2. BUT CELEBRATING A LOST TOOTH IS A LONGSTANDING UNIVERSAL TRADITION.

While the specific concept of a fairy is recent, cultures around the world have been commemorating lost baby teeth for hundreds of years. In the 13th century, Islamic scholar Ibn Abi el-Hadid referenced the Middle Eastern tradition of throwing a baby tooth into the sky (or "to the sun") and praying for a better tooth to replace it. Throwing teeth is a common practice: in Turkey, Mexico, and Greece, children traditionally toss their baby teeth onto the roof of their house. In India, Korea, Vietnam, and the Philippines, lower teeth are thrown upward but teeth from the upper jaw are thrown to the floor, to encourage the new adult teeth to grow straight. Traditions aren't always sunny, though—Norwegian and Finnish children are warned of Hammaspeikko, the "tooth troll" who comes for children who don’t brush.

3. EVEN THE VIKINGS PRIZED BABY TEETH.

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Think the Vikings were too busy pillaging to celebrate baby teeth? In fact, the Norse Eddas—myths, verse, and poetry from 13th century Scandinavia—make reference to the tand-fé ("tooth fee"), a small payment from parent to child to recognize the other side of the milestone—when an infant's first tooth came in. The ancient poem "Grimnismal" even notes that Alfheim, the "fairy world" in Norse mythology, was given to their god Frey as a "tooth gift" in his youth. According to various sources, some Viking warriors would later wear their children’s teeth as talismans, believing they’d bestow luck and protection in battle.

4. SOMETIMES THE FAIRY IS A MOUSE.

Many global baby-tooth traditions are tied to rodents. Psychiatrist and physician Leo Kanner’s 1928 study "Folklore of the Teeth" references children offering their lost baby teeth to mice, rats, squirrels, or other animals known to have sturdy teeth. In Spain, author Luis Coloma developed the character El Ratoncito Pérez as a Tooth Fairy analog for the boy-king Alfonso XIII. El Ratoncito Pérez is still popular in most Spanish-speaking countries today, and has even appeared in modern marketing campaigns for Colgate toothpaste. Likewise, in France and Belgium, children wait for La Petite Souris ("the little mouse") and leave him not only baby teeth, but morsels of cheese as well.

5. THE AVERAGE AMERICAN TOOTH IS CURRENTLY WORTH AROUND $3.19.

What’s a tooth worth? According to an annual survey conducted by Visa, 32 percent of children receive a single dollar, which is by far the most common amount. But 5 percent of children received $20 or more, bringing the nationwide average to $3.19 [PDF]. Unsurprisingly, the value of a tooth is tied not only to family income level, but geographic region—the Tooth Fairy tends to be more generous in the Northeast and stingier in the South and West. Confused about how much to give your sweet dreamer? Visa now provides a helpful calculator to check what other children in their demographic are receiving.

6. THE VALUE OF TEETH FLUCTUATES WITH THE MARKET.

Insurance group Delta Dental has also been tracking average Tooth Fairy rewards since 1998, and comparing their results to stock market activity. They've found that in 12 of the past 13 years, trends in Tooth Fairy payouts have correlated to movement in the S&P 500. Their study also notes that in 2015, the Tooth Fairy gave out a total of $256 million dollars—that’s a lot of teeth!

7. ROSEMARY WELLS WAS AMERICA’S FOREMOST TOOTH FAIRY EXPERT …

In the 1970s, Northwestern University professor Rosemary Wells realized that while the practice of replacing baby teeth with money was extremely popular, little was known about the origins of the Tooth Fairy. Wells took it upon herself to interview anthropologists, parents, and children; write a series of magazine articles exploring the roots of the character; and conduct a national survey of 2000 parents to learn more about families’ various traditions and interpretations. Her fascination with the topic even led to an appearance on The Oprah Winfrey Show, and she had her business cards labeled with "Tooth Fairy Consultant."

8. … AND SHE FOUNDED THE TOOTH FAIRY MUSEUM IN DEERFIELD, ILLINOIS.

Dr. Wells's Tooth Fairy research led to her amassing a sizable collection of memorabilia, and in 1993 she turned her split-level suburban home in Deerfield, IL into the Tooth Fairy Museum. A popular choice for local elementary school field trips, the museum contained art, dolls, books, and other memorabilia celebrating depictions of the Tooth Fairy across various cultures. The museum closed following Dr. Wells's death in 2000.

9. THE FAIRY CAN HELP PROMOTE HEALTHY HABITS.

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In addition to commemorating a milestone, many parents now use the Tooth Fairy as a means of promoting good dental hygiene from a young age. Vicki Lansky, author of more than two dozen parenting and household books, cleverly suggests, "Let your child know early on that the tooth fairy pays more for a perfect [tooth] than for a decayed one." Other parents have gotten creative with conditional gifts—like a note promising an extra $20 if the child brushed her teeth every day after lunch for a month.

10. NO ONE’S QUITE SURE WHAT THE TOOTH FAIRY LOOKS LIKE …

Unlike Santa, there isn’t a widely-held consensus on the Fairy’s appearance. Most cartoons and books depict a winged female sprite or pixie, much like Tinkerbell, bearing a wand and trailing sparkles in her wake. But Dr. Wells's 1984 survey found that while 74 percent of Americans viewed the Tooth Fairy as female, another 12 percent envisioned the Fairy as neither male nor female. Other responders gave less traditional answers: some imagined the Tooth Fairy as a bear, a bat, a dragon, or even "a potbellied, cigar smoking, jeans clad tiny flying male."

11. … WHICH MIGHT EXPLAIN A WIDE VARIETY OF CASTING CHOICES.

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The Tooth Fairy is a recurring character in modern cinema, and has been portrayed by a diverse assortment of actors and actresses. The 2010 comedy Tooth Fairy cast former wrestler Dwayne "The Rock" Johnson as a bruising hockey star who is pressed into Fairy-duty; the 2012 straight-to-video sequel re-used the concept with comedian Larry the Cable Guy in the title role. Veteran actor Art LaFleur donned the wings for both The Santa Clause 2 and The Santa Clause 3. Meanwhile, actress Isla Fisher voiced an animated (and extremely birdlike) version of the Tooth Fairy for the 2012 Golden-Globe nominated film Rise of the Guardians, while Amy Sedaris played a delightfully deranged version on the kiddie show Yo Gabba Gabba!

12. THE TOOTH FAIRY INSPIRED A PROMINENT SKEPTIC.

As a fictional character, you wouldn’t expect the Tooth Fairy to appear in many serious publications. But Dr. Harriet Hall, an Air Force flight surgeon, skeptic, and critic of alternative medicine, has coined the term "Tooth Fairy Science" to describe the importance of ensuring a phenomenon actually exists before studying it. Dr. Hall offers this fantastic example of how a carefully crafted experiment may still yield an invalid result:

If you don’t consider prior probability, you can end up doing what I call Tooth Fairy Science. You can study whether leaving the tooth in a baggie generates more Tooth Fairy money than leaving it wrapped in Kleenex. You can study the average money left for the first tooth versus the last tooth. You can correlate Tooth Fairy proceeds with parental income. You can get reliable data that are reproducible, consistent, and statistically significant. You think you have learned something about the Tooth Fairy. But you haven’t. Your data has another explanation, parental behavior, that you haven’t even considered. You have deceived yourself by trying to do research on something that doesn’t exist.

13. NATIONAL TOOTH FAIRY DAY IS FEBRUARY 28 (OR MAYBE AUGUST 22?)

According to no less an authority than www.toothfairy.org, National Tooth Fairy Day is celebrated annually on February 28. However, other sources and calendars also list the holiday on August 22. (With such a busy schedule, the Fairy surely deserves two days, right?) The second week of August is also recognized as National Smile Week (to promote dental health) so a follow-up celebration for the Tooth Fairy seems appropriate. (But the cynics among us might note that February 27 is Sword Swallower's Day [PDF], so perhaps the Fairy has some extra work to do.)