In 1928, the UK physicist Paul Dirac stumbled on an equation that seemed to show that, for every particle, there’s another, nearly identical particle with an opposite electric charge. Just four years later, the US physicist Carl David Anderson proved Dirac’s prediction correct by capturing a picture of a ‘positron’ – a particle with the same size and mass as an electron, but with a positive charge rather than a negative one. This rapid series of developments unlocked one of the most momentous and enduring conundrums of physics: if particles with opposite electric charges annihilate one another when they meet, why is there any matter left? And if there’s no more matter than antimatter in existence, then the Universe should have annihilated itself soon after the Big Bang – yet, here we are. This brief animation breaks down this extraordinary, nearly century-long science puzzle, detailing some of the surprising explanations posited by contemporary physicists.