Recent studies show that the so called “jump to contact” phenomenon, which often happens between a sharp tip and a flat surface in close proximity and results in formation of a neck between the two, is probably the origin of friction. By studying the phenomenon with a scanning- tunneling microscope (STM) and monitoring the conductance evolution, we have found that such necks- between the STM tip and the Pb(110) sample surface, after being stretched to a certain degree, may- shrink spontaneously till its break. The fact that surface cleanness and temperature have- significant influence on the shrinking process suggests that the process is a result of surface- diffusion of Pb atoms.