incubate
verb
°To brood, raise, or maintain eggs, organisms, or living tissue through the provision of ideal environmental conditions.
"1985: Cormac McCarthy, Blood Meridian, New York, Vintage International, May 1992, page 3 - The mother dead these fourteen years did incubate in her own bosom the creature who would carry her off."
°To incubate metaphorically; to ponder an idea slowly and deliberately as if in preparation for hatching it.