Light mesons are an excellent tool with which to study non-perturbative quantum chromodynamics
(QCD), since the quark masses are negligible compared to the mass of the composite system.
They are also the only system that offers spin exotic quantum numbers, which point directly to
hybrid systems. Although highly excited states of light mesons have often been reported, they
have rarely been confirmed. The diffractive excitation of pions and kaons, as studied in the
COMPASS experiment at very high energies, allows us to address these issues with unprecedented
statistical precision. We present the first clear observations of highly excited mesons in terms
of spin (𝐽max = 6) and mass (𝑀meson ≈2600 GeV/𝑐2), thus probing the strong interaction in the
confinement regime. We also present the first evidence of a crypto-exotic strange meson