Conservation of Mass and Energy
With the introduction of atomic theory and a more complete understanding of the nature of both matter and energy, it was found that a relationship exists between these two concepts. Einstein formulated the Law of Conservation of Mass and Energy. This states that matter and energy are interchangeable under special conditions. The conditions have been created in nuclear reactors and accelerators, and the law has been verified (obviously). This relationship can be expressed by Einstein's famous equation:
E = mc2
Energy = Mass x (Velocity of light)2 (squared)