The standard model of particle physics is a well-tested theoretical framework, but there are still a number of issues that deserve further experimental and theoretical investigation. For quark physics, such issues include the nature of quark confinement; the mechanism that connects the quarks and gluons of the standard model theory to the strongly interacting particles; and the weak decays of quarks, which may provide insights into new physics mechanisms responsible for the matter–antimatter asymmetry of the Universe. These issues are addressed by the Beijing Spectrometer III (BESIII) experiment at the Beijing Electron–Positron Collider II (BEPCII) storage ring, which for the past decade has been studying particles produced in electron–positron collisions in the tau-charm energy-threshold region, and has by now accumulated the world’s largest dataset that enables searches for non-standard hadrons, weak decays of the charmed particles and new physics phenomena beyond the standard model. Here, we review the contributions of BESIII to such studies and discuss future prospects for BESIII and other experiments.