Implosion is a process in which objects are destroyed by collapsing (or being squeezed in) on themselves. The opposite of explosion, implosion concentrates matter and energy. True implosion usually involves a difference between internal (lower) and external (higher) pressure, or inward and outward forces, that is so large that the structure collapses inward into itself. An example of implosion is a submarine being crushed from the outside by the hydrostatic pressure of the surrounding water.