Gillette has created what they believe to be the world’s smallest advertisements. The ads – which measure less than 100 microns in size – were written onto actual male hairs using an electron microscope.

Related Fact: Later in life, razor mogul King Camp Gillette became a strong proponent of utopian socialism and planned a community in Arizona in which engineers would rationally orchestrate all activity. Gillette even offered Teddy Roosevelt $1 million to serve as president of this planned utopia in 1910, but Roosevelt declined.

[Sources: DVICE and Engineering ToolBox. See previous Numbers of the Day here. ]