Milde interessant: der stetige Ausbau des Berliner S- und U-Bahnnetzes in den letzten 120 Jahren.
The nomenclature, line colours, and routes of the services, especially for S-Bahn, have constantly changed throughout history. The video only highlights major opening, suspension of the tracks in service and does not show minor name changes, route changes, etc. I did try to capture the route and name changes of the lines as much as possible, but the video may not accurately represent the actual routes of the lines at that time as there are not enough records of these changes. Hence, these changes only happen in the background and are not shown as a separate event.
For the colours, the lines are shown in the colours that are used today unless they were previously part of a different line. (For e.g. current Line U4 was initially green as it was part of Line B, then changed to blue as it was designated as a separate Line 4 in 1966, then changed again to yellow for better visibility. In this video, the colour only changes in 1966 from green to yellow.)