After earning his associate's degree, Muren began working as a visual effects Artist full-time. In 1976, Muren was hired at Industrial Light & Magic (ILM), then an upstart visual effects studio founded by George Lucas. Lucas' and ILM's first film, Star Wars, was released in 1977 to wide critical and public acclaim and was the highest-grossing film of all time up until that point. In 1985 he worked on the visual effects of the Disney theme park’s Captain EO the American 3D/4D science fiction film starring Michael Jackson, directed by Francis Ford Coppola and the executive Producer was George Lucas.