Like the previous image, this Hubble tuning fork diagram splits galaxies according to their morphology into spiral, elliptical and lenticular galaxies. But unlike today's galaxies, these are small and still not fully formed. They do, however, have distinct color and structure. "This is a key question: when and over what timescale did the Hubble Sequence form? To do this you need to peer at distant galaxies and compare them to their closer relatives, to see if they too can be described in the same way," said author Lee.