The movement of protons through electrically charged water is one of the most fundamental processes in chemistry. It is evident in everything from eyesight to energy storage to rocket fuel—and scientists have known about it for more than 200 years.

But no one has ever seen it happen. Or precisely measured it on a microscopic scale.

Now, the Mark Johnson lab at Yale has—for the first time—set benchmarks for how long it takes protons to move through six charged water molecules. The discovery, made possible with a highly customized mass spectrometer that has taken years to refine, could have far-reaching applications for researchers in years to come.