Casimir Effect is what happens when 2 mirrors are placed parallel to each other in empty space. The mirrors are mutually attracted to each other due to the presence of Vacuum. This phenomenon was predicted by Dutch Scientist Hendrik Casimir in Eindhoven. The force between the 2 mirrors is referred to as Casimir Force. This effect can be easily understood with the analogy of considering the gap prevalent between the 2 mirrors as a cavity. All electromagnetic fields have a spectrum characteristic of different frequencies while free Vacuum has equal frequencies referred to as cavity resonance. All Micro Electro Mechanical systems make use of this effect to a great extent.