Just under our skin, the human body is packed full of weird, wonderful and occasionally off-putting features which all add up to create a person's unique appearance.
We've been trying to figure out how our bodies work since pretty much the dawn of time, and all that big thinking has likely been accompanied by some contemplative chin stroking.
Speaking of chins, you might have noticed that the people in your life have rather different looking ones and you might be wondering why that is.
Instead of spending all your conversations with your nearest and dearest staring at their chins and contemplating the wonders of biology, we'll spare you the time and just tell you.
Or rather, we're going to tell you what a TikToker who talks about biology has to say on the matter, because they seem to know what they're talking about.
TikToker Hank Green was responding to another content creator who was wondering what chin dimples were and what caused them - when he gave an explanation.
"It's in your chin and it is very weird", he began.
"You have identified correctly a weird muscle. Well done. Almost every muscle in your body connects a bone to another bone. Your bones yank on each other, that's how you move."
"There are other muscles, like sphincters, that just yank on themselves. The heart is a totally different kind of muscle - it yanks on itself to pump your blood around."
"In our faces, we have a bunch of muscles that do not connect to other bones. You can tell this, right? Like, all the movement that faces do, we that we can talk and emote and stuff - we're not yanking on bones here. We're yanking on skin."
If the phrase 'yanking on skin' wasn't grossing you out, it's time to delve into the magnificent matters of the mentalis muscle, which as you might have guessed, is located in your chin.
Green explained that the mentalis muscle connects from bone to skin, so when you flex it that's what causes dimples to appear and you can use it for facial expressions.
The TikToker showed off diagrams of the mentalis muscle and how it worked, though not everyone in the audience was thrilled at what they saw.
He said: "You can see the mentalis here, doing an absolutely wild thing, sticking all of its little muscle fibres into your skin.
"When you contract that muscle, it yanks. It yanks on the skin and makes those little dimples.
"It's a little weird. We're all made out of meat."
More than a few people felt like they could have done without knowing that, asking the TikToker to 'never speak of this again' while another complained that it 'makes me nauseous'.
A third said they were 'so upset that I now know this information' while others said their newfound knowledge would 'haunt' them for a while.