NASA announced today that the Hubble Space Telescope has snapped baby pictures of the “primordial” universe about 600 million years after the Big Bang, the earliest images ever.

Branded as “time machine” photos, the images show the young universe when it was about 13 billion years old and reveal “a primordial population of compact and ultra-blue galaxies that have never been seen before.” Blue indicates a lack of heavy elements and therefore the galaxies’ youth.

Says lead astronomer Garth Illingworth of the University of California-Santa Cruz: “We’re seeing very small galaxies that are seeds of the great galaxies today.”

As for the significance? According to the news release, “the deep observations demonstrate the progressive buildup of galaxies and provide further support for the hierarchical model of galaxy assembly where small objects accrete mass, or merge, to form bigger objects over a smooth and steady but dramatic process of collision and agglomeration. It’s like streams merging into tributaries and then into a bay.”