Just as a sonar device sends out sound waves in order to explore the hidden depths of the ocean, electrons can be used in the same way by scanning tunnelling microscopes to investigate the concealed properties of the atomic lattice of metals.
Seeing the Fermi Surface in Real Space by Nanoscale Electron Focusing;
Weismann et al.;
Science (2009), DOI: 10.1126/science.1168738