Scientists have discovered six unusual structures at Earth's core-mantle boundary (CMB), the region where Earth's solid mantle meets its liquid outer core. This finding comes from a study published in the Journal of Geophysical Research: Solid Earth, which used deep learning techniques to analyze over 2 million seismic recordings collected from 1990 to 2024. These recordings were gathered from seismic stations around the world and used a specific type of seismic wave known as PKP precursors—very faint waves that arrive before the stronger seismic waves—to study the CMB. These precursors are sensitive to subtle changes in the Earth's interior, making them useful for detecting structures that are otherwise hard to see. Previously, such structures were only observed as isolated patches, but the study now reveals them as continuous belts of heterogeneity—areas where the material properties differ from their surroundings. These newly identified regions are located beneath the North Atlantic, northern Eurasia, the South Atlantic, Southern Africa, the Pacific, and around Antarctica. The researchers caution that the maps they have created show probable scattering regions rather than exact outlines of hidden structures. This is because the precursor signals used in the study cannot pinpoint a scatterer with precision from a single seismic station. The study highlights that while the current findings are significant, there is still much to learn about the CMB. The researchers suggest that future studies could combine their new catalog of structures with other types of seismic waves to create more detailed images of the boundary. Additionally, using dense networks of seismic sensors could help scientists determine the exact locations of these structures with greater accuracy. This research contributes to a growing understanding of Earth's deep interior, which is crucial for studying processes like mantle convection, the movement of tectonic plates, and the dynamics of the Earth's magnetic field. As technology and data analysis methods improve, scientists hope to uncover more about the hidden complexities of our planet's interior.