An ordinary microscope, which employs optical lenses, could view objects
    smaller than the wavelength of light. An electron microscope could view 
    smaller things with greater clarity than an optical microscope, but still
    could not clearly view individual atoms.
    
    So Binnig and Rohrer decided to build their own instrument – something new 
    that would be capable of seeing and manipulating atoms at the nanoscale level.
    To do that, they began experimenting with tunneling, a quantum phenomenon in 
    which atoms escape the surface of a solid to form a kind of cloud that hovers 
    above the surface; when another surface approaches, its atomic cloud overlaps 
    and an atomic exchange occurs.
    
    By maneuvering a sharp metal conducting tip over the surface of a sample at an
    extremely small distance, Binnig and Rohrer found that the amount of electrical
    current flowing between the tip and the surface could be measured. Variations in
    this current could provide information about the inner structure and the
    height-relief of the surface. And from this information, one could build a
    three-dimensional atomic-scale map of the sample’s surface.