An overview is given on recent experiments on molecular rectification and on molecular single electron transistors. It is argued that it is often difficult to assign the observed properties to the molecules in question in an unambiguous way. Therefore, investigations of larger molecule-like objects, namely of carbon nanotubes are presented. From scanning tunneling spectroscopy the density of states of pure carbon nanotubes and of boron doped nanotubes has been determined as a first step in this direction.