The XYZ states revisited

The BESIII and the LHCb became the leading experiments in the study of the exotic states after the Belle and BaBar experiments finished their data taking in the first decade of this century. We review the progress in the study of the XYZ states at BESIII and LHCb experiments with their unique data samples in [Formula: see text] annihilation at center-of-mass energies of 3.8–4.6 GeV and in [Formula: see text] collision at center-of-mass energies 7, 8, and 13 TeV, respectively. With these data samples, we have deepened our understanding of the most famous charmonium-like states [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text], as well as other similar states like the [Formula: see text] and [Formula: see text]. We review the progress in the study of these states and also discuss perspectives at future experiments.