Scientists at CERN spent the last decade waiting for a one-in-ten-billion chance event, and now they’ll spend the next few years figuring out whether it challenges the laws that (we think) govern the smallest building blocks of matter.

Most people who aren’t particle physicists have probably never heard of a kaon, but this tiny subatomic particle could present a big challenge to the Standard Model: the theory that describes the fundamental forces of nature and names all the smallest building blocks of matter, or elementary particles. University of Birmingham physicist Evgueni Goudzovski and his colleagues spent about a decade watching what happened when kaons decayed, and they found that about 1.3 times out of 10 billion, a decaying kaon splits into another subatomic particle called a pion, along with a pair of extremely small, elusive particles called a neutrino and an anti-neutrino. (The rest of the time, kaons decay into different products.)

That’s a staggeringly rare event. As such, it took physicists an extremely long time to see it in action. But the Standard Model predicts it should be even rarer: less than 1 in 10 billion. Figuring out the difference could reveal something fundamental about how the universe works — something we’ve been missing for decades.

Goudzovski and his colleagues presented their work during a recent seminar at CERN.

The Substance is a movie of escalating violence. It was born from director Coralie Fargeat’s beliefs about aging in a society that only values women for their youth and beauty. Its eponymous pharmaceutical requires its takers to birth a younger double out of their spine, their backs splitting open in a fantastic shower of blood and viscera. And, naturally, it ends in one of the wildest, goriest, unhinged body-horror scenes you’ll ever see on the silver screen.

“It explodes in the face of the audience, which represents the world,” Fargeat tells Inverse.

If you’ve seen The Substance, you probably have some questions about the wild finale. Luckily, we had a chance to talk to the writer-director, so we had her break down the movie’s final moments, how they came together, and what it all means.