In 1933 it was determined by Walter Meissner and Robert Ochsenfeld that superconductive materials can repel magnetic fields. They determined that when a material was penetrated with a magnetic field, in its' superconductive state, it would create a current inside the superconductor. Because there is almost zero resistance in the material at its' Tc temperature, the current creates an opposing magnetic field that exactly balances the originating field. When the material's temperature becomes higher than its' Tc value the magnetic field simply pass through it. This was an extraordinary discovery and thus the term "Meissner Effect" was coined to describe this unexpected occurrence.