Atomic force microscopy image of a single silicon adatom, size 660 pm x 660 pm x 120 pm. The two crescents are interpreted to represent two orbitals originating in a single tip atom.

Giessibl, Hembacher, Bielefeldt and Mannhart. Science 289, 422 (2000).

Image courtesy: Drs. Jochen Mannhart, Franz Giessibl, University of Augsburg, Germany.