Scientists have discovered something under our skin, between our muscles and organs, around our veins and arteries, and lining our lungs. In fact, it’s almost everywhere. Researchers are calling it the “interstitium.” It’s a layer of fluid-filled compartments that looks like a mesh. Researchers once thought it was just connective tissue, but now they think it might be an organ. They used a tiny camera probe to look around the living human body. Learning more about the interstitium and its purpose might help scientists detect cancer earlier. They might be able to stop it from spreading in the body.