Muography

Primary cosmic rays, such as protons arriving from space, collide with oxygen and nitrogen molecules in the atmosphere, producing elementary particles called muons. Muons reach the Earth's surface at a rate of about one per second per area the size of a human palm.
Muons possess a high penetrating power, allowing them to pass through massive structures on the scale of several kilometers. However, as the density-length of the material they traverse (the product of its average density and path length) increases, the number of muons that pass through the material decreases. Muography leverages this property to non-destructively visualize the internal structure of large objects such as volcanoes and pyramids. Advances in detector performance and miniaturization have expanded its applications to a wide range of fields, including resource exploration, disaster prevention and infrastructure monitoring.