When Jurassic Park debuted in 1993, computer generated special effects were barely out of their cradle. A handful of films such as Terminator 2 had dabbled in using digital animation for very specific effects, but no one had yet been able to crack the Holy Grail—making these effects look believably real on giant movie theater screens.

With Steven Spielberg’s dinosaur blockbuster, the effects world took a brontosaurus-sized leap forward into a realm where creatures born on desktop computers could hold their own alongside flesh and blood actors. This behind-the-scenes video from The Academy of Motion Pictures Arts and Sciences gives a glimpse of how Jurassic Park broke wide open the landscape of what was possible in film. The video is an installment of Moments That Changed the Movies, a new Academy Originals web series, debuting Monday.

Today, Jurassic’s towering T-Rex and sleek raptors are still considered examples of top-notch digital effects, but when Spielberg began working on the film, computer effects were still so untested that all involved assumed the film’s dinosaurs would be created largely with animatronic robots. It took a handful of wizards at Industrial Light and Magic (ILM) to convince Spielberg’s team that computer-generated creatures could work even better.

In the end, Jurassic Park featured only 15 minutes of dinosaur footage. But those handful of minutes changed film forever. Suddenly, anything a director could dream up could be put on the screen – tornadoes, snarling monsters and, as we’ve seen nearly ever summer since, wide-scale devastation. But just 21 years ago, the idea of accomplishing such feats was science fiction itself.