What is there left to learn about the Drosophila clock?

Circadian rhythms offer probably the best understanding of how genes control behavior, and much of this understanding has come from studies in Drosophila. More recently, genetic manipulation of clock neurons in Drosophila has helped identify how daily patterns of activity are programed by different clock neuron groups. Here, we review some of the more recent findings on the fly molecular clock and ask what more the fly model can offer to circadian biologists.