The early universe, fresh from the Big Bang, was a hot, dense soup of simple elements: hydrogen, helium, and trace amounts of lithium. But within a cosmic blink—just 100 to 200 million years after the birth of the universe—water began to form.

Water may have first formed 100–200 million years after the Big Bang, according to a modeling paper published in Nature Astronomy. The authors suggest that the formation of water may have occurred in the universe earlier than previously thought and may have been a key constituent of the first galaxies.