  A universal mechanism of superconductivity applicable to ``low temperature''
and ``high temperature'' superconductors is proposed in this paper. With this
model of mechanism experimental facts of superconductors can be qualitatively
explained. A function is introduced to describe the average separation distance
between vibrating lattice atoms, which is crucial for the transition from
normal to superconductive state. However, the most attractive and exciting
conclusion that can be derived from this physical picture, is that given atoms
of other element be successfully sandwiched between ferromagnetic atoms one by
one, a superconductor constructed this way is most likely to have a very high
transition temperature.
