Two-dimensional materials such as graphene and transition metal dichalcogenide monolayers exhibit unique physical properties resulting from their reduced dimensionality and crystal symmetry. Their optical properties are governed by excitons, i.e. electron and hole pairs bound by Coulomb interaction. Although only a few dozen of layered compounds have been successfully synthesized, more than 5000 materials with different properties are predicted to be stable as atomically thin layers. They can be assembled by simple stacking to form heterostructures and provide an additional avenue to engineer new properties in a desired fashion.

I will present what we can learn from linear and nonlinear optical spectroscopy in atomically thin semiconductors for applications in optoelectronics and photonics, exploring also spin and valley properties. I will show recent investigations of optical transitions with carriers residing in different layers, resulting in interlayer excitons whose transition energies can be tuned by external fields. Approaches to confine excitonic states for applications in quantum technology will be discussed and future research opportunities in this multidisciplinary field will be outlined.