What if there was another universe in that atom? If time is proportionate to space, their several billion year cosmic evolution might pass in the blink of an eye. What type of object or organism would our "universal atom" be inside of? I always thought this was a fun one...
PS: several levels were skipped for the sake of a simple diagram. A scientifically plausible version would have to reconcile the moons and sub-atomic particles as well.