A diamond anvil cell is a laboratory tool for creating enormous pressure in a very small space. Two diamonds face one another across a tiny sample held in a gasket. Tightening the apparatus concentrates force on the diamonds’ small flat tips, which can subject the material to conditions far beyond those in everyday life.
Diamond is both exceptionally hard and transparent to many kinds of light. Researchers can therefore examine the compressed sample with optical instruments and X-rays while it remains under pressure. They may also heat or cool the sample to investigate how its structure and electrical behavior change under different conditions.
The device is central to research on hydrogen-rich superconductors because some proposed or observed superconducting states require pressures of tens or hundreds of gigapascals. Researchers can measure electrical resistance and other properties inside the cell, but the tiny sample size makes some measurements difficult and calls for careful experimental controls.
A result achieved inside a diamond anvil cell is not automatically usable outside one. Ask what pressure the experiment required, whether the material was measured after pressure release, and whether the claimed transition was supported by more than a single resistance measurement.