Gillette took a step away from the "plaster ads on every surface in the civilized world" school of marketing to do something pretty cool. They rounded up a few doctors of electron microscopy and had them stick a whole ad on a strand of hair.
The hair used in the ads actually came directly off of the face of a fully grown man. The water and soap were then filtered off, leaving pure manface hair to be shoved into the electron microscope. From there, they were blasted with ions to imprint the actual ads and photographed under the microscope. The ads measure about 100 microns across, which translates into tenth of a millimeter, and pending Guinness confirmation makes them the world's smallest ads.
And that would be cool enough. Great ad, guys. But Gillette decided that they wanted to take it a step beyond the print and poster campaign, so they sent the actual hairs to airport bathrooms with accompanying QR codes on the installations so passersby could see the full-sized ads. Which is kind of cool, I guess, but do you really want your brand to be associated with the hair found in the mens bathrooms at airports? [Copyranter]