This volume provides backgrounds, methods, and troubleshooting for the analysis of circadian rhythms at the molecular, cellular, and organismal levels in vertebrates and invertebrates, and also covers light input, sleep, circalunar rhythms, and seasonal rhythms. It discusses behavioral and biological testing, histochemistry, single-cell imaging, electrophysiology, photochemistry, genetics, genomics, transcriptomics, proteomics, metabolomics, systems biology, chemical biology, and mathematical modeling.