Satyres en atlante, a 2nd century sculpture at the Louvre. Gregg Tavares/CC BY 2.0

A version of this post originally appeared on Tedium, a twice-weekly newsletter that hunts for the end of the long tail.

Back in 2010, Graham Barker, an Australian librarian, announced that after spending 26 years collecting belly-button lint —basically because he was bored and curious—he had set a Guinness World Record.

Barker’s collection (you can see it in pictures here) is pretty gross, but his long-running experiment does speak to a basic human interest in our navels, which are one of the few things that separate us, from, say, androids. Or, as Barker put it: “The raw material is worthless but as a unique world record collection and a piece of cultural heritage, of debatable merit, it has some curiosity value,” he explained then in an interview with the Daily Mail.

But belly buttons are more than just a physical quirk, they are also one of the few body parts to have inspired a phrase, and perhaps even a philosophy: navel-gazing, or the act of contemplating yourself too much.

Navels are all about lint and self-interest, in other words, something Barker, for one, managed to combine into the same pursuit.

Barker’s experiment might have been amateur, but actual scientists have devoted a fair amount of energy to uncovering the mysteries of belly buttons, like why, exactly, all that lint gets stuck there in the first place.

It turns out, for example, that men are more likely than woman to get belly button lint, according to research done by Dr. Karl Kruszelnicki, a popular Australian scientist who won an Ig Nobel Prize in 2002 for a far reaching study of nearly 5,000 belly buttons. The reason? Men are more likely to have hair on their stomachs. Kruszelnicki also adds that there’s a certain reason why specific colors usually pop up. “The reason it is usually blue is that we mostly wear blue or grey trousers, often jeans, and when these rub against the body, the fibers often end up finding their way to the navel,” Kruszelnicki told the Telegraph in 2009.

Which also means, if you buy a new undershirt, plan for a little extra belly lint. A University of Vienna researcher figured this out by analyzing his own belly button. Seems like a reasonable use of his time.

On the more useful research front, a 2013 study in the British Journal of Surgery finds that if you’re going to get an appendectomy, the best spot to get one could be through the navel, because the end result limits the amount of noticeable scarring.

On the less useful research front, a 2014 study by the American Society for Aesthetic Plastic Surgery found that an oval-shaped belly button is considered most attractive, but the study was done before the rise of the dad bod, so there’s a chance this research is out of date.

And, finally, one Duke University study said that the placement of a navel can be a key to whether you’ll be successful or even any good at sports, since the placement of the navel acts as your center of gravity.

Still, a body’s belly button—essentially an umbilical scar—might just be a physical oddity without a widely known cultural concept tied to it, which, in this case, is omphaloskepsis, or navel-gazing. The word itself has roots in Greek, and while originally it was seen as something like meditation, it’s now something much more banal, even disparaging—shorthand for overthinking, thinking of nothing in particular besides oneself (like, perhaps, this article.)

But how did belly buttons get involved at all? A large part of the reason can be blamed on Robert Alfred Vaughan, who made the first printed reference to gazing at one’s navel in the 1856 book Hours With the Mystics. In a section of the book highlighting monks around Greece’s Mount Athos, he wrote:

“It seems that some of the monks (called, if I mistake not, Hesychasts) held that if a man shut himself up in a corner of his cell, with his chin upon his breast, turning his thoughts inward, gazing towards his navel, and centering all the strength of his mind on the region of the heart; and, not discouraged by at first perceiving only dark- ness, held out at this strange inlooking for several days and nights, he would at length behold a divine glory, and see him- self luminous with the very light which was manifested on Mount Tabor. They call these devotees Navel-contemplators. A sorry business! All the monks, for lack of aught else to do, were by the ears about it, either trying the same or reviling it.”

So basically, because some guy mocked a bunch of monks for focusing on their navels in a religious sense, we’ve got a phrase about staring at one’s belly button.

Elsewhere, though, belly buttons get more respect, like in yoga, where one’s navel chakra—a spot on the spine directly behind your navel—is considered an important energy center. Which is certainly a better fate than the target of all your self-absorbed thoughts.

A version of this post originally appeared on Tedium, a twice-weekly newsletter that hunts for the end of the long tail.