Here is a video showing all the modifications made to the source code of Android from the start to Ice Cream Sandwich :
The graph represents the source tree (which uses git). Non-leaf nodes are directories and leaf nodes are files where their color represents the type of file. Files appear as they are modified and disappear if they are not touched for 2.5 seconds.
In other words, each “blast” from a user is a commit. These commits come from both Googlers and contributors. The data was taken from stitching together the logs of all the many AOSP (Android Open Source Projects) projects using a software called gource