Since the pioneering work of Woodcock in the 1950's, the importance of giant aerosol particles to warm rain formation has been studied and debated. On the one hand, their large size relative to other CCN implies that they could accelerate precipitation onset, while on the other, their limited number compared to smaller CCN suggests that they may not have a significant effect on the precipitation produced. Recent findings of the author, and others, suggest that the number of CCN can modulate the importance of the giant aerosol particles to warm rain formation both in warm stratiform and cumuliform clouds. New microphysical calculations are presented to understand and isolate the conditions under which smaller CCN versus giant aerosol particles are important to warm rain formation, providing guidance for how precipitation in future climates may be modulated by anthropogenic sources of CCN. New findings are also presented relating the influence of urban areas on giant aerosol particle concentrations in the atmosphere, and suggestions for future areas of research are discussed.