The smallest thing in the world. You could not see it even with a super telescope.

Internet persona(s) who happens to follow you and you happen to follow them back and maintain communication with and have a mutual liking for eachother whether it be friendship wise, etc. (Mutuals if more than one mutual)

is very small

The empire state building

is perfectly fine :)

(this is in contrast to EVERY other definition of this)

The smallest thing in the world.

Microscopic.