 Abstract circadian clocks are internal biological clocks that regulate daily rhythms in physiology and behaviour. They are controlled by a master clock located in the hypothalamus, which regulates other clocks throughout the body. Disruption of circadian rhythm can lead to various health problems such as sleep disorders, metabolic diseases, and even cancer. Recent research has revealed that circadian clocks are regulated at the level of chromatin structure, suggesting that they may be more complex than previously thought. This knowledge could lead to better treatments for chronobiologically related diseases.