Why was Germany divided into East and West Germany?

In the period from 1949 till 1990, Germany was split in east and west. Why was there a West and East Germany created? In this video I will explain how and why it came to that split. Link to the Cecilienhof Palace in Potsdam: Credits: • Marshall plan picture: E. Spreckmeester, published Economic Cooperation Administration - Source, Publiek domein, • Hier hilft der Marshall plan foto: Par Bundesarchiv, Bild 183-20671-0014 / CC-BY-SA 3.0, CC BY-SA 3.0 de, • D-Mark: By National Museum of American History - Image by Godot13, Public Domain, • 100 DM: Alliierte Militärbehörde in Deutschland, Public domain, via Wikimedia Commons