Hi,
I think the smallest geometrics is a 100 pin VQFP and 32 pin TSSOP. The last the most difficult due to the distance between the rows. It's a good help to be nearsighted , at least when you are as old as I am.
TOK
Gorgon the Caretaker - Character in a childrens TV-show from 1968.
Hi.
Any size, down to a housefly shoe size every day.
It's done under the microscope. The utensils are fine pins, for positioning.
The soldering iron tip size is not of much concern, it is the techniques of using flux and wicking and managing surface tension of molten solder.
Miguel