From the Canon Imaging Plaza YouTube Channel:
See what's deep inside the EF200-400mm F4L IS USM Extender 1.4x. Made up of hundreds of precise mechanical and optical parts, the EF200-400mm F4L IS USM Extender 1.4x is a super telephoto lens that opened up new possibilities for professionals on the front line of sports, nature and news photography.
Canon unveils the precise inner construction of this L lens that has not been visualized before. This video was filmed using stop motion animation method.