It’s not every day that you get to discover an organ.

Researchers at University Hospital Limerick recently published a new paper in The Lancet Gastroenterology & Hepatology. In it, they identified an organ that’s been hiding under our noses, well, since our existence. Is it just me, or is the human body is far more complex than most of us give it credit for?

Here’s what you need to know about the newly classified human organ.

1. It’s called the mesentery.

This double-folded liner can be found within the abdominal cavity, beginning at the pancreas. According to Discover Magazine, it acts as a sort of belt, securing both the small and large intestines to the wall of the abdomen.

2. It has, of course, been there the whole time.

This isn’t actually a “new” organ. In fact, it was described as early as 1508, by Leonardo da Vinci himself. The researchers believe that all humans possess this organ, which is necessary to live.

3. But it’s been ignored for centuries now.

According to J. Calvin Coffey, who authored the study, the anatomists of previous centuries got the mesentery wrong. Coffey found that important medical texts offered inaccurate descriptions of the mesentery, calling it fragmented and disjointed when his research showed that it’s actually one “continuous structure.”

That’s enough to fit the criteria for an organ.

4. Important medical textbooks—including Gray’s Anatomy—are now being updated to include it.

Moving forward, medical students will learn to identify and treat the mesentery as a unique organ. Hopefully, treating it as an organ will help both doctors and researchers to identify its role in digestive diseases, such as Crohn’s or irritable bowel disease.

5. But it’s function is still unknown.

With the mesentery’s anatomy and structure detailed in the research paper, Coffey believes that the next logical step is to try to understand the organ’s function.

6. But the discovery could have important implications.

According to Coffey, understanding function is the best way to identify abnormal function. In other words, if you can figure out what a healthy version of the organ does, you can also figure out what happens when disease takes hold.

7. The mesentery is now one of 79 organs in the human body.

Though Coffey has stated that he’s not certain if there’s an official procedure when it comes to identifying and naming “new” organs, his peer-reviewed research seems to have gained widespread acceptance. So, can you name all 79 organs? Don’t worry — most people can’t.

8. The vitals are still the most widely recognized organs.

The kidneys, liver, lungs, brain, and heart make up the vital organs. But while they are indeed vital, numerous other organs play an important role in crucial processes such as digestion, reproduction, and circulation, to name a few.

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