We begin to pry out the rear light, a cable keeps it in place, but it does give us access to some hidden screws. This in turn grants us access to the internals.
This massive umbilical leads from the charging port to the batteries and the BMS (Battery Management System) at the other end, and an LED board behind the rear light.
We peel out said circuit board and discover some secrets. This guy controls the rear LED array, as well as some status LEDs along the top of the tube (probably to indicate battery activity).