  We optically detect the positions of single neutral cesium atoms stored in a
standing wave dipole trap with a sub-wavelength resolution of 143 nm rms. The
distance between two simultaneously trapped atoms is measured with an even
higher precision of 36 nm rms. We resolve the discreteness of the interatomic
distances due to the 532 nm spatial period of the standing wave potential and
infer the exact number of trapping potential wells separating the atoms.
Finally, combining an initial position detection with a controlled transport,
we place single atoms at a predetermined position along the trap axis to within
300 nm rms.
