After hydrogen and helium, lithium is the lightest and simplest element in the universe. It should have been everywhere right after the Big Bang...but the data shows a mysterious shortage. The explanation may point to an unlikely dark matter candidate.

Located some 11 billion light-years from Earth are two clouds of gas. Just two billion years younger than the Big Bang itself, they appear to be the first known clouds that are completely unaltered since the birth of the universe.