How Did Milliken Measure This?

In the early 1900s, Milliken measured how much electric force was needed to make drops of oil levitate. But that only works if each drop is the size of one electron, right? Like if you have a whole cluster of things with electrons, would you still notice that kind of discrete electric field? Yeah, you can have a whole oil drop. What he's measuring is the ionization of that drop, like essentially, how many non-neutral particles are in that drop. That's what's going to affect the force that the drop feels when it gets put into an electric field.