They help to create everything from spaceships to superheroes and alien cities to entire planets.
But some visual effects workers in the UK aren't happy.
They say they're overworked and underappreciated, while film studios make millions from the work they provide.
Miguel Santana is 23 and relatively new to the industry.
He says it's a stressful job, one he loves and he "wouldn't have it any other way".
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