TheCodeBreakers
This was
invisible under normal circumstances but glowed when exposed to
ultraviolet light. But with newspapers being carried as third-class mail,'
this was hardly the fastest method of getting information to where it was
going.
The Germans then came up with what F.B.I. Director J. Edgar Hoover
called "the enemy's masterpiece of espionage." This was the microdot, a
photograph the size of a printed period that reproduced with perfect
clarity a standard-sized typewritten letter. Though microphotographs (of
a lesser reduction) had carried messages to beleaguered Paris as far back
as 1870, a tip to the F.B.I, in January of 1940 by a double agent, "Watch
out for the dots—lots and lots of little dots," threw the bureau into a near
panic. Agents feverishly looked everywhere for some evidence of them,
but it was not until August of 1941 that a laboratory technician saw a
sudden tiny gleam on the surface of an envelope carried by a suspected
annaabi.ee 
