The Hubble Space Telescope still isn't done giving up secrets of the early universe. Researchers using the Atacama Large Millimeter/submillimeter Array (ALMA) have discovered that a patch of 10 billion-year-old galaxies in Hubble's Ultra Deep Field view holds gas that helps explain the "Golden Age" of galaxy and star formation. This first completely "blind" (that is, not expecting anything) 3D millimeter wavelength search of the old universe turned up galaxies with an abundance of carbon monoxide, a hint that they were rich in the molecular gas key to creating stars.
Combined with Hubble's visible and infrared light data, the ALMA search forms a much more complete picture of galaxy formation. Astronomers could even create a 3D map of the universe's star-forming potential, transitioning from a young period (where those gas-laden galaxies were common) to today. There's a promise of more, too. The Ultra Deep Field study covered a slice of sky for 50 hours, but a future initiative, the ALMA Spectroscopic Survey in the Hubble UDF, should cover a larger area over 150 hours. You may hear much more about the history of the cosmos in the near future.