To improve their adaptation to the changing environment presents on Earth, organisms from bacteria to mammals have evolved a timing system that anticipates these changes. This endogenous timing system, called the circadian clock, orchestrates most aspects of physiology and behavior. The mammalian circadian clock is hierarchically organized. A central clock localized in the Suprachiasmatic Nucleus (SCN) of the hypothalamus is daily synchronized by the light via the retina-hypothalamus tract and coordinates the peripheral clocks localized in peripheral tissues. The SCN synchronizes most aspects of circadian physiology and is required to keep phase coherence between the different peripheral organs. However, our new results suggest that peripheral clocks can feedback on the central clock and influence global circadian physiology. This feedback of peripheral tissues on the central clock could explain the circadian disruption observed in many diseases and could play a role in the development of these diseases.