The Atom-Probe Field Ion Microscope was introduced in 1967 at the 14th Field Emission Symposium in Gaithersburg, Maryland. The Atom-Probe was, and remains, the only instrument capable of determining “the nature of one single atom seen on a metal surface and selected from neighboring atoms at the discretion of the observer”. The development of the Atom-Probe is a story that highlights Erwin Muller's strong and sometimes volatile personality. It is a story of an instrument that one NSF proposal reviewer called “impossible” because “single atoms could not be detected”. It is also the story of the Field Emission Laboratory at Penn State in the late 1960s and the contributions of two superb technicians, Gerald Fowler and Brooks McLane, and two graduate students, Douglas Barofsky and John Panitz. The anecdotes from this time are colorful and reflect Erwin's pedigree as Gustav Hertz's student in the Berlin of the 1930s.