From ferocious velociraptors to killer gorillas, author Michael Crichton’s characters faced some difficult battles, but Crichton himself had his own secret battle.

The best-selling author and filmmaker passed away from cancer at the age of 66 on Tuesday morning in Los Angeles.

Crichton is best known for his fiction works like “Jurassic Park” and “Congo,” many of which were turned into motion pictures. He also started the long-time running television series “ER.”

The prolific author broke into mainstream success with “The Andromeda Strain” in 1969. His most recent work was 2006’s “Next.”

Other works have included “The Great Train Robbery,” “Eaters of the Dead,” “Sphere,” “The Lost World,” “Timeline,” “Prey” and “State of Fear.”

As a graduate from Harvard Medical School, many of his works were inspired by his biological and computer studies. He even wrote the non-fiction “Five Patients: The Hospital Explained.”

“The world knew him as a great storyteller that challenged our preconceived notions about the world around us – and entertained us all while doing so,” said a statement by his family on his official Web site.

Fortunately, his work will live on in the hearts and minds of his fans.