When Lucas wanted to make Star Wars the technology to create the things he wanted to show on screen didn't exist, so he started a company to invent the technology he needed.
It was called Industrial Light and Magic (ILM) and after inventing the technology to make spaceships and lightsabers seem real, it worked on lots of other films.
Harry Potter and Prisoner of Azkaban, Pirates of the Caribbean and Jurassic Park any many, many other films all owe the success of their computer generated effects to ILM.
Lucas also wanted his films to sound better than others, so started a sound company that was later named Skywalker Sound to make the sound effects for Star Wars.
But having created the sounds for his films, Lucas wanted his films to sound right in cinemas, so started yet another company, called THX to produce sound in a way he was happy with.
In recent years Lucas has been looking at the ways cinemas get the film onto the screen, moving into something called digital projection.
That means using computers to put the film onto screen, rather than shining light through a piece of film like most cinemas.