Unravelling the mechanisms of learning and memory can, and should, be tackled at many levels. Discovery of the huge family of odourant receptor genes provided olfaction with 'molecular' respectability similar to that afforded to the visual system. Consequently, molecular studies have dominated the olfactory literature this past year, even to the point of providing a molecular basis of olfactory perception. Needless to say, the molecular approach favours a 'hard-wired' system; however, other results suggest that flexibility in the olfactory system provides for certain adaptations that are crucial to the biological needs of mammals.