The Sleeper

Questions of the day among certain operatives:

How do you "wake" a sleeper cell "up" without destroying the cell? There is search for the "trigger" that activates the sleeper, but can it be reversed? Can the trigger be redesigned or pulled back? Does it include hypnotic manipulation or can it be a direct contact? If it's the former, how deep is a hypnotic level is needed before the subject can be manipulated for years? If it's the latter, how can it be just a simple phrase that would recapsule the hypnotic suggestions that have been embedded in the mind for so long?

Lots to think about, huh, dudes?