Holography is a three dimensional photographic procedure using coherent light properties (interferences produced by two laser beams) which give a perfect duplicate of the object recorded thanks to the encoding of light. Whereas photography are taking using daylight, laserlight is indispensable to create a hologram. Ordinary light is composed of flux of photons with very variables caracteristics and emitted at any moments. In contrast, the laser emits a coherent beam of light, meaning : - monochromatic (all the photons have the same frequencie or color) - the waves have the same direction (spatial coherence) - the are in phase (temporale coherence) A hologram is created by the intersecting beams of a laser into a holographic emulsion (plate) which come from the same laser. The first, or reference beam, is guided to the plate, the second, to the object which is to be transformed into a hologram. Light waves from the object are reflected toward holographic plate. The converging of the two beams create an interference pattern which brings informations concerning the form of the object and its position in space. After development, illuminated by laser light, at the same angle as the reference beam, the objects appears to be suspended in space in its original location. Holography recreates the original waves, exactly identical as the object from a waves of reference.