Up until the late 1920, all animated films were silent films. The oldest full-length film still in existence is The Adventures of Prince Achmed, from Germany. It used stop-motion photography to film shadows as if they were moving on their own. Meanwhile, in the United States, Walt Disney had already invented Mickey Mouse, which became a national phenomenon. In 1928, Disney used a process of synchronizing picture and sound to create the very first animated short with audio: Steamboat Willie. The outstanding welcoming of Mickey Mouse into the lives of people all over the world caused Disney to start creating new characters, including Pluto, Donald Duck, Goofy, Minnie Mouse, Daisy Duck, and many others. In 1932, Disney created the world's first color cartoon: Flowers and Trees.

Disney wasn't satisfied with just working with the technology availabe: he started inventing his own. In 1936, he patented an invention called "The Multi-Plane Camera", which allowed for a three-dimentional view of an animated film. His first short film to use this device was The Old Mill, though the technology would become more prominent in movies like Snow White and Bambi.

Speaking of movies, this is the part you've all been waiting for. In 1937, Walt Disney released America's very first animated feature-length movie, and the first to use cell animation: Snow White and the Seven Dwarfs. This is widely considered today to be "The One that Started It All."