ELI5: Explain Like I'm 5

Philtrum

Do you know that part of your face where your nose and lips meet? That's called the philtrum! It's the little groove people have there.

When you were still in your mommy's tummy, your face was forming and that's when your philtrum was made. It's formed by the two sides of your face coming together and fusing in the middle.

Some people have a deeper philtrum than other people, but it doesn't really affect anything. You can't see it all the time because our noses and mouths cover it up, but it's still a part of our faces and everyone has one!