Bright light and Sunlight.
Circadian rhythms are described as being self-sustained and endogenous which persist in the absence of any environmental cues such as the light or dark cycle. These rhythms are in the close approach due to the period of the earth’s rotation. They are frequently attributed to as the "body clock,". This rhythm acts like the cycle which tells our bodies when to rest, arise, and eat and use to manage many physiological processes. This inner body clock is influenced by environmental cues such as sunlight and temperature.