Quasiparticles are common in condensed-matter physics, but now it is possible to do collider experiments with them. Fabian Langer of the University of Regensburg in Germany and colleagues used femtosecond optical pulses to create excitonic electron–hole pairs in an insulated tungsten diselenide, and then used a strong terahertz field to accelerate and collide electrons with holes. Emitted photons reveal the details of the collisions, which include annihilation events analogous to those found in high-energy electron–positron collisions.