Circadian rhythms are one of the most amazing and intriguing adaptations of life on earth. They are internal biological cycles that follow an approximately 24-h period, allowing plants to anticipate and adapt to daily environmental changes. These rhythms are governed by an endogenous clock that integrates external cues such as light, temperature, and humidity to regulate various physiological and developmental processes. Circadian rhythms regulate many plant processes, for example, in their preparation for dawn, plants accumulate key components of the photosynthetic machinery. Meanwhile, leaves or flowers frequently close before nightfall, shielding delicate tissues from cooler night time temperatures. This clock has a sophisticated mechanism with three key components namely input, the core oscillator and output mechanisms. Over the past years, powerful advances in molecular genetics have uncovered the molecular mechanisms underlying the cellular circadian clockwork. The key components in Arabidopsis have been studied extensively and help in developing a generalized understanding of the key mechanisms of the clock.