Chronobiology describes the rhythmic processes used by organisms to time behaviors and physiological processes. It focuses on cycles, biological rhythms, and organisms' adaptive abilities to cycles that occur in nature (such as solar and lunar cycles).
An organism's life is comprised of various cycles and rhythms. Research on chronobiology include various subjects areas such as menstrual cycles, animal migration patterns, sleep cycles, and reactions to lightness and darkness.
A well-known chronobiological function is the circadian rhythm which in humans regulates our sleep/awake cycles, energy regulation, and when we eat.