Researchers have made new discoveries about the in-between spaces in the human body, and some say it’s time to rewrite the anatomy books.

A study published in Scientific Reports this week described a fluid-filled, 3-D latticework of collagen and elastin connective tissue that can be found all over the body, in or near our lungs, skin, digestive tracts and arteries.

It’s a hard thing to describe, and the New York University School of Medicine did it in several ways in a news release on Tuesday: a “series of spaces,” a “highway of moving fluid” and “a previously unknown feature of human anatomy.”

It said the study’s authors referred to the system as “an organ in its own right,” though not all researchers agree with that characterization.