In all of the research literature I have read so far, I've seen colloid thrusters explained as devices that gain thrust by releasing only charged droplets from ionic liquids as the exhaust mass. Electrospray phenomenon can also generate individual ions. If colloid and electrospray thrusters are the same (as written in many places on the internet and elsewhere), how do some electrospray thrusters also release ions as exhaust mass? How are these thrusters actually classified? Under which circumstances are only droplets/only ions used and under which circumstances both droplets and ions? For example, if you were to model a plume from an electrospray thruster's emitter, would you consider both droplets and ions or only ions/only droplets in the plume? And how is FEEP thruster different from these two types? I am so confused.