Our experimental studies and a set of the published data allow one to conclude that animals and humans can perceive visible light not only with mediation of the visual sensory system, but also due to the existence of specific extraocular photoreceptors. In the latter system, we can classify three separate stable levels of interaction with exogeneous electromagnetic waves (EMW) of the visible range. The first, most simple level is the cellular level (cells possessing sensor proteins reactable to EMW). The next, higher level is based on interaction of EVW with specialized electromagnetoreceptors; acupuncture points and meridians providing the maintenance of electromagnetic homeostasis of the organism cam be considered such a receptor system. Finally, the most complex level involves specialized sensory pathways and central brain structures controlling general homeostasis of the organism with mediation of the processes of metabolism.