Today’s Wonder of the Day was inspired by Bethanie. Bethanie Wonders, “Why are some bellybuttons innies and some outies?” Thanks for WONDERing with us, Bethanie!

So are you an innie or an outie? What are we talking about? Belly buttons, of course! So which one are you? An innie or an outie?

Go ahead. Take a peek. It's OK if you don't remember offhand. As their names imply, innie belly buttons go inward, while outie belly buttons stick out. Which one do you have?

If you're like most people, you probably have an innie belly button. Don't worry, though, if yours is an outie. There are plenty of people with outie belly buttons, too. But what's the deal with belly buttons anyway? What are they for and why do some go in while others stick out?

If you've been born, it doesn't matter whether you're a baby, a kid, or an adult. Your belly button is pretty much useless. Sure, it collects lint and dirt from time to time. If you're in a pinch, it might hold just enough ketchup (or is it catsup?) for a small order of French fries. But for the most part, it's just there.

Before you were born was when you really used your belly button. Well, sort of…The belly button marks the spot where the umbilical cord connected your body to your mother's womb.

The umbilical cord was your life line when you were inside your mother's womb. It was a rope-like cord with blood vessels that connected your baby belly to your mother's placenta inside her womb. Nutrients and oxygen flowed to your body through the umbilical cord, and wastes your body needed to get rid of flowed back to the placenta.

When you were born, the doctor tied off or clamped the umbilical cord, so that it could be cut off where it attached to your belly. Over the first few weeks of your life, what was left of the umbilical cord slowly dried up and fell off. What was left? Your belly button!

Whether you end up with an innie or an outie is usually a matter of chance. Most people end up with innies, but some people have outies. Outies usually occur when more of the umbilical cord is left when it's cut, leading to more skin left over once it dries out.

In some rare cases, outies are caused by a condition known as an umbilical hernia. An umbilical hernia occurs when a part of the intestine pokes through the muscles in your belly and pops out through the belly button. This condition often goes away on its own within the first year of life. If it does not, however, surgery is sometimes needed to fix the condition.

When it comes to belly buttons, us human beings are not alone. Monkeys and other mammals have belly buttons, too. Even though they're useless to us once we're born, they do serve as a good reminder of the circle of life that brought us into the world.

Sometimes you may hear the belly button referred to as the navel. That's just another name for belly button. In fact, one of your favorite fruits borrows that name. Have you ever seen or eaten a navel orange? We bet you have! Navel oranges have a circle that forms on their outer layer of skin. It looks kind of like an outie belly button, thus the name navel orange. The outie belly button on a navel orange is caused by a second baby orange growing inside the fully-grown orange!

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