The universe is filled with a mysterious invisible substance - dark matter. Scientists think this was produced during the Big Bang, at the same time as all the other particles.
Due to the effect of gravity, clouds of dark matter collapsed in on themselves, forming foam-like structures, which pulled in clouds of hydrogen and helium gas.
Eventually, these gas clouds grew so dense that nuclear reactions started inside them, making the first stars shine. The latest scientific evidence suggests the universe’s first stars were born around 200-300 million years after the Big Bang.