  Investigation into the properties and structure of unstable nuclei far from
stability remains a key avenue of research in modern nuclear physics. These
efforts are motivated by the continual observation of unexpected structure
phenomena in nuclei with unusual proton-to-neutron ratios. In recent decades,
laser spectroscopy techniques have made significant contributions in our
understanding of exotic nuclei in different mass regions encompassing almost
the entire nuclear chart. This is achieved through determining multiple
fundamental properties of nuclear ground and isomeric states, such as nuclear
spins, magnetic dipole and electric quadrupole moments and charge radii, via
the measurement of hyperfine structures and isotope shifts in the atomic or
ionic spectra of the nuclei of interest. These properties, when measured with
sufficient precision for a long range of isotopes, offer prominent tests of
recently developed state-of-the-art theory and help to stimulate new
developments to improve the many-body methods and nucleon-nucleon interactions
at the core of these models. With the aim of exploring more exotic short-lived
nuclei located ever closer to the proton and neutron driplines, laser
spectroscopy techniques, with their continuous technological developments
towards higher resolution and higher sensitivity, are extensively employed at
current- and next-generation radioactive ion beam facilities worldwide. Ongoing
efforts in parallel promise to make even more exotic species available for
study at next-generation facilities. Very recently, an innovative application
of laser spectroscopy on molecules containing short-lived nuclei has been
demonstrated offering additional opportunities for several fields of research,
e.g. fundamental symmetry studies and astrophysics.
