“ARGON! Up, up! Come on, boy, let's go!” Don Eigler, a
researcher at IBM's Almaden Research Centre in California, is
one of the world's experts in moving atoms. In 1989, he spelled
out the letters “IBM” in xenon atoms, which made him the first
person to move atoms individually. But today he is having
trouble persuading his large Leonberger dog to get up from the
office floor.  If dogs were as easy to move as atoms, Mr Eigler
would be able to get Argon out of the office by using a computer
mouse to point, click and drag him. But although the ability to
move individual atoms is impressive, it is not particularly
useful for anyone but experimental scientists like Mr Eigler.
Most researchers think that moving atoms one by one will not be
a practical way of creating new materials.  A better way may be
to exploit the natural tendencies of atoms and molecules to
crystallise, fold, form layers or otherwise self-assemble.
Ordered molecular structures arise spontaneously, for example in
crystallisation or in the format