Scientists have used a laser to tickle atoms of antimatter and make them shine, a key step toward answering one of the great riddles of the universe.

Researchers at the European Organization for Nuclear Research, or CERN, spent decades figuring out how to create an antimatter version of the most basic atom — hydrogen — and trap it for long enough to perform tests.

In a paper published online Monday by the journal Nature, they reported that when antihydrogen is stimulated with a laser it produces light on the same ultraviolet frequency as hydrogen.

Scientists are ultimately hoping to understand the subtle difference that explains why the universe is made of matter, even though the Big Bang produced an equal amount of antimatter and the two cancel each other out.