The origin of large scale magnetic fields found in galaxies and clusters of galaxies is still a mystery. Researchers from National Astronomical Observatory, Princeton university, Toshiba Corporation and University of Tokyo have found that cosmological density fluctuations, which explain a variety of large scale structures in the universe, can also generate large scale magnetic fields by the cosmological recombination age of 370 thousand years from the Big Bang. These fields are large enough to be amplified to those observed in galaxies at present, and may have affected primordial star formation in the early universe.