For fifty years, physicists have pursued a particle that exists only where force meets itself — a glueball, made not of matter but of the very glue that holds matter together. At a collider in Beijing, an international team has now gathered the strongest evidence yet that this exotic object is real, confirming a cornerstone prediction of quantum chromodynamics. The discovery does not merely add a particle to a list; it suggests that the universe permits forms of existence that have no analog in the world we can touch or see.