One (photon), two(-dimensional crystals), a lot (of potential): a quick snapshot of a rapidly evolving field

We present a concise overview of the state of affairs in the development of single-photon sources based on two-dimensional (2D) crystals, focusing in particular on transition-metal dichalcogenides and hexagonal boron nitride. We briefly discuss the current level of advancement (i) in our understanding of the microscopic origin of the quantum emitters (QEs) identified in these two material systems, and (ii) in the characterisation of the optical properties of these emitters; then, we survey the main methods developed to enable the dynamic control of the QEs' emission energy. Finally, we summarise the main results stemming from the coupling of QEs embedded in 2D materials with photonic and plasmonic structures.