Figure 3.

Importance of assaying rhythms at a single-cell resolution. To be considered circadian, a rhythm must be maintained under constant conditions. When examining rhythms at the tissue level in which the tissue is composed of multiple cells, it is important to realize that the absence of rhythmicity under constant conditions could be attributable to two possibilities: either the loss of rhythmicity (indicating the rhythm is not circadian) or desynchrony among oscillators. In the latter case, individual rhythms may actually be circadian; however, the assay has insufficient resolution to show the presence of rhythmicity. To distinguish between the two possibilities, assays sensitive to the functional unit of rhythms generation must be used.