Exotic helium atoms that contain the antimatter counterpart of protons, or a meson consisting of a quark and an antiquark, are studied by laser spectroscopy. By comparing the atomic transition frequencies with quantum electrodynamics calculations, the properties of antimatter and mesonic matter may be determined at the highest possible precision. This allows us to probe some of the fundamental symmetries of nature. In the field of particle physics, there is heightened interest in metrological frequency measurement techniques in view of similar future experiments at particle accelerator facilities such as the new Extra Low Energy Antiproton (ELENA) ring of CERN and the Ring Cyclotron of Paul Scherrer Institute.