  Quantum technologies have seen a rapid developmental surge over the last
couple of years. Though often overshadowed by quantum computation, quantum
sensors show tremendous potential for widespread applications in chemistry and
biology. One system stands out in particular: the nitrogen-vacancy (NV) center
in diamond, an atomic-sized sensor allowing the detection of nuclear magnetic
resonance (NMR) signals at unprecedented length scales down to a single proton.
In this article, we review the fundamentals of NV center-based quantum sensing
and its distinct impact on nano- to microscale NMR spectroscopy. Furthermore,
we highlight and discuss possible future applications of this novel technology
ranging from energy research, material science, or single-cell biology, but
also associated challenges of these rapidly developing NMR sensors.
