Researchers from the Carnegie Institution of Washington and Ecole Normale Supérieure de Lyon in France have announced the results of experiments that will enable geophysicists to better understand the rotation and magnetism of the Earth's inner core. Reporting in the June 2 issue of Science, the team resolves a standing debate over the properties of hexagonal close-packed iron at extreme pressure. The scientists compressed polycrystalline iron samples to pressures of 15 to 152 GPa. Anvil cells constructed of ultrapure synthetic diamond reduced background luminescence and scattering by the setup. The 488- and 514.5-nm lines from an argon-ion laser excited the sample, and a single-grating spectrometer with holographic notch filters collected the Raman spectra.