The importance of circadian clocks for understanding how organisms function is acknowledged this year with the award of the Nobel Prize in Physiology or Medicine. The unveiling of the intricate molecular processes governing rhythm generation has now set the stage to understand the complex regulation of the circadian system in the "real world"; in nature animals simultaneously experience multiple biotic and a-biotic cues that may differentially affect central and peripheral pacemakers. This multidisciplinary workshop will cover recent advances in research on plasticity in circadian rhythms and sleep in insects, fishes, birds, and mammals, both in the laboratory and in the field.