According to the Big Bang theory, all of the matter and energy of the Universe was released in a single explosion. Afterward, it expanded and cooled enough to form atoms of the lightest elements: hydrogen, helium, and some lithium. In the present Universe though, there are considerably more elements that are all heavier and could only have formed as a result of nuclear fusion. Identifying when this fusion occurred has been difficult though because you have to find the most distant and oldest objects in the Universe to do so, but that is exactly what researchers at MIT, the California Institute of Technology, and the University of California at San Diego have done.
A quasar some 13 billion light years away was discovered last year, and is one of the further objects ever discovered. It dates back to when the Universe was a mere 750 million years old. The researchers decided to aim a telescope at quasar 3C 279 and capture the spectral data for its light. Thanks to the quantum nature of atoms, every element emits different frequencies of light, so by analyzing the spectrum of some light source, you can determine what elements are there. Determining what elements are not there is a much more difficult task though, as every explanation for why they are not there must be disproven.
That is exactly what the researchers did though, allowing them to confidently state that this quasar is the first object discovered from the first epoch of star formation. This is such an early time that the elements fused in the first stars has not been released into the Universe and seeded the cosmos. One object is not enough to characterize that epoch though, so now the researchers are searching for more of the extremely old and distant quasars.