This paper sets out to try to determine some of the nanoscopic details of template action in zeolites. The problem has been addressed by monitoring the effects of competitive templating using, in particular, atomic force microscopy and high-resolution scanning electron microscopy. Using these techniques, it is possible to determine the subtle crystal growth changes that occur as a result of altering the concentration of these competitive templating agents. This work concerns the two important intergrowth systems MFI-MEL and FAU-EMT. It was found that some organic templating agents provide much greater structure-directing specificity. So much so in the case of the MFI-MEL system that a 2 mol% doping with the highly specific tetrapropylammonium cation drastically changes the fundamental growth processes. Furthermore, the effect of template crowding is shown to reduce specificity. This work shows how extensive frustrated intergrowth structures can still be accommodated within a nominal zeolite single crystal.