Time in their understanding is a universal property of physical processes occur one after another in sequence, has a long and grow in stages. And if living beings have "a sense of time ", a kind of biological clock? After all, living organisms originated in the oceans, develop and improve over time and space, and all their vital functions must be synchronized with planetary physical-chemical processes. "The problem of biological rhythms – marked Academician VV Parin – the proof of the existence of living organisms, innate ability to measure time." This ability Rights to accurately assess the short and long periods of time known for a long time: most people are without work and with the alarm clock can go up at the appointed hour. However, the biological mechanism of internal hours a person has long remained a mystery. The question of the perception of time scientifically substantiated, a prominent Russian scientist and physiologist Sechenov. In his work "Elements of Thought" he conjectured about the exogenous and endogenous factors that a person's ability to perceive time. Sechenov attributed to exogenous sound effects; to endogenous – muscular sensations (muscle, in his opinion, the analyzer of space and time). But then this problem has not received intensive development. Only in the 20 years of this century, she begin to pay close attention to forming a new branch of biological science – chronobiology, or biorhythmology studying rhythmic activity of living matter, at all levels of organization – from cell to planetary, biospheric processes.