Chronobiology: principles and methods.

Chronobiology is a discipline whose principles consider time as an essential dimension of biological phenomena. The reason of this resides in a relativistic vision of biological dynamism for which space, mass, energy and time are properties of dynamic events. Biological time may be linear (chronological time) and cyclical (period time). Chronobiology considers the biological events whose expression is periodic with several kinds of periodicities (biological rhythms). Because of bioperiodic events, a methodology for approaching cycling functions is needed. Chronobiometry is illustrated as an important part for understanding how biological rhythms can be investigated.