 There is something paradigmatic about molecular biology and also something revolutionary about its rapid progress and expansion. It is not clear how to characterize this and similar developments. Was this a Kuhnian revolution? It did involve major social and intellectual reorganization, one that conflicted with the previous ones in some respects but without undermining the Darwinian paradigm. Quite the contrary. Or is molecular biology more like a style of scientific practice than a paradigm? Such an explosive development as molecular biology hardly fits Kuhn’s description of steady, normal scientific articulation of the new paradigm by puzzle solving. Instead, it seems better to regard it as a large toolkit of methods or techniques applicable to several specialty fields rather than as an integrative theory-framework within one field.