The world's smallest smiley

This atomic smiley is written on a Ag(111) surface by manipulating individual silver atoms extracted from the native surface with the STM-tip. It has a radius of 18 nm. It is probably the world smallest smiley. It is created for public outreach, especially for the kids to inspire nanoscience. The big smile of this smiley is generated by surface electron standing waves. Yes, at the nanoscale, the electron can behave not only as a particle but also as a wave, a famous phenomenon known as wave particle duality. That is why we can see the electrons as water waves here creating a big smile.
  Category: Fabrication technique
  Source: Ohio University/Hla Group