A leaf of paper was about a hundred thousand nanometers thick; a third of 
a million atoms could fit into this span. Smart paper consisted of a network of 
infinitesimal computers sandwiched between mediatrons. A mediatron was a thing 
that could change its color from place to place; two of them accounted for 
about two-thirds of the paper's thickness, leaving an internal gap wide enough 
to contain structures a hundred thousand atoms wide.