Circadian rhythm is the biological process critical to the well-being of living organisms, from plants to insects and mammals. The circadian rhythms oscillate with a period of approximately 24 hours due to the 24-hour light-darkness pattern of the solar day. Some physiological processes, such as alertness regulation and hormone production, are related with circadian rhythm. Circadian disruption, as experienced by night shift workers, travelers across multiple time zones, submariners or miners, can lead to lower productivity, sleep disorder, and more serious health problems.