Endogenous circadian clock integrates cyclic signals of environment and daily and seasonal behaviors of organisms to achieve spatiotemporal synchronization, which greatly improves genetic diversity and fitness of species. This review ad-dresses recent studies on the plant circadian system in the field of chronobiology, covering topics on molecular mechanisms, internal and external Zeitgebers, and hierarchical regulation of physiological outputs. The architecture of the circadian clock involves the autoregulatory tran-scriptional feedback loops, post-translational modifications of core oscillators, and epigenetic modifications of DNA and histones. Here, light, temperature, humidity, and internal elemental nu-trients are summarized to illustrate the sensitivity of the circadian clock to timing cues. In addition, the circadian clock runs cell-autonomously, driving independent circadian rhythms in various tissues. The core oscillators responds to each other with biochemical factors including calcium ions, mineral nutrients, photosynthetic products, and hormones. We describe clock components sequentially expressed during a 24-h day that regulate rhythmic growth, aging, immune re-sponse, and resistance to biotic and abiotic stresses. Notably, more data have suggested the circadian clock links chrono-culture to key agro-nomic traits in crops.