Superclusters themselves form even larger structures, called "filaments", "complexes", "walls" or "sheets", like the Great Wall. These may span between several hundred million light-years to 10 billion light-years, and cover more than 5% of the observable universe. Superclusters suggest something about the initial condition of the universe when these superclusters were formed. The directions of the rotational axes of galaxies within superclusters may also tell us about the formation of galaxies early in the history of the Universe.