Unknown TypeUnknown LevelUnknown LocationUnknown InhabitantsUnknown A galaxy filament is a type of naturally-occuring cosmological structure composed of thousands to millions of gravitationally bound galaxies stretched out into a strand over dozens to hundreds of megaparsecs. Between them are voids, and they become thinner and less well-defined as a universe expands and these voids get larger. Just about any imaginable types of galaxy can be found in a filament, and in large numbers.