Whilst Welles didn't invent the techniques he used, he put them together in such a way that created an incredible work of art. Whether it's seeing the Nurse walking through the door relected in the shattered snow globe, or the dancing girls reflected in the window whilst Welles and Cotton chat around the table, or the use of the massive fireplace in the Kane mansion, or the use of the ceilings throughout, or Kane standing in front of his huge poster while he speaks from the lectern...wherever you pause this film, each frame is beautifully and perfectly conceived. You could write an entire thesis on one mise-en-scene from Citizen Kane; there are very few films about which you could say the same.
"He may look like an idiot and talk like an idiot but don't let that fool you. He really is an idiot."