I have come to CERN’s campus, near Geneva, Switzerland, to see the experiment, called the Symmetry Tests in Experiments with Portable antiprotons (STEP), in its final preparations before the big day, as project leader Christian Smorra shows me around the facility.“It’s groundbreaking for antimatter science,” he says. “The idea of transporting antiprotons existed, in principle, since the time when this facility started, and now it’s the first time that it has become possible to actually do that.”