Since the introduction of sound, special effects have constantly improved over time. Special effects are techniques used to make realistic imitations of events that cannot actually be filmed, such as a monster destroying a city. Sometimes, as in scenes of mass destruction and mayhem, it is useful to build a scale model of a city or building which is actually very small. Since close-up shots of the model make it look actual size, film makers do not have to destroy the real thing. Another technique is the use of a blue screen.
Film producers can record action in front of a screen which is an unusual shade of blue.
The reason it is blue is that this specific color will only be in the background. Afterwards it would be possible to film a background separately and use it in place of the blue areas in the background. Finally, today's technology allows artists to create realistic three dimensional models of objects and people with computers. The film industry constantly uses these principles and many others. The art and science of film making continue to advance even today.