Nuclear magnetic resonance (NMR) spectroscopy is a widely used tool for chemical analysis and molecular structure recognition. Because it typically relies on the weak magnetic fields produced by a small thermal nuclear spin polarization, NMR suffers from poor sensitivity compared to other analytical techniques. A conventional NMR apparatus typically uses large sample volumes of about a milliliter—large enough to contain around a million biological cells.
Source:
https://phys.org/news/2020-06-quantum-technique-high-resolution-nuclear-magnetic.html