It’s not often that you see 50-year-old equipment in a modern physics laboratory, let alone find it at the center of cutting-edge research. But then, most such labs aren’t run by Ronald Walsworth.

A senior physicist at the Harvard-Smithsonian Center for Astrophysics and a member of the physics department faculty, Walsworth, along with postdoctoral fellows David Glenn and Dominik Bucher, developed a system that uses nitrogen-vacancy centers (atomic-scale impurities in diamonds) to read the nuclear magnetic resonance (NMR) signals produced by samples as small as a single cell. And they did it on a shoestring budget using an old, donated electromagnet.

The system will enable researchers to peer into previously unseen biological processes as well as the chemical properties of materials, and could help open the door to answers to a host of new questions in fields ranging from condensed-matter physics to chemistry to neurobiology. The work is described in a paper recently published in Nature.

“This gives us for the first time a tool for conducting NMR on samples that are similar to the volume of a single cell, while still maintaining high spectral resolution,” Walsworth said. “There are two major challenges we address with this work. There’s the spatial size, or the volume of the samples, and the other is the spectral resolution. To do useful NMR spectroscopy at these small scales, you need to have both.”

The difficulty in achieving both, Walsworth said, is partly related to the way NMR operates.

Discovered at Harvard in the 1940s, NMR works by exciting the atoms in a sample by using powerful magnetic fields and measuring the radio frequencies they emit. Since each molecule emits specific frequencies, chemists and physicists have learned to read those radio spectra to learn everything from the material properties of various molecules to how proteins are folded.