In other words, the middle of nowhere — the loneliest place in the universe. They’re called cosmic voids. Even inside of galaxies space is almost completely empty; on the order of 1 atom per cubic centimeter and a star every few lightyears. Cosmic voids aren’t perfectly empty, just a lot emptier than the galaxy-laden regions of the galactic filaments. Our understanding of cosmic voids is growing rapidly, but there’s still a hell of a lot to learn.