A team of international scientists, led by astronomers from Cardiff University, has unravelled the history of galaxies for the first time.
Researchers discovered galaxies can change their structure over the course of their lifetime.
They also found 83% of all stars formed since the Big Bang were in a disc-shaped galaxy but today only 49% are; the rest are in oval-shaped galaxies.
Their research was carried out using the Hubble and Herschel telescopes.
Prof Steve Eales, from Cardiff University's school of physics and astronomy, said it was the first time this "metamorphosis" had been accurately measured.
"Galaxies are the basic building blocks of the universe, so this metamorphosis really does represent one of the most significant changes in its appearance and properties in the last eight billion years," he added.