From BBC News:

Nano circuit offers big promise

The first computer circuit to be built on a single molecule has been unveiled by researchers in the US.  It was assembled on a single carbon nanotube, a standard component of any nanotechnologist’s toolkit.

The circuit is less than a fifth of the width of a human hair and can only be seen through an electron microscope.

(more here)

Wow thats small,  but whats the market for this?   I know some short and small people, but no one small enough to be able to use a computer thats the size of a human hair.