Scientists Have Discovered a New Organ in the Human Body. What is the Interstitium?

The bubble wrap-like network only became visible when the pathologists used a new laser endoscope, called a confocal laser endomicroscope, that allowed them to see microscopic tissues in living people. Most studies of tissues missed the interstitium because they rely on biopsies of tissues that are then dried and fixed onto microscope slides; the desiccated samples never showed the fluid-filled spaces.