The mini-review gives special attention to holistic approach and mechanisms of processes. The physical and chemical frames and background for visual perception and signaling are discussed. Perception of photons by retinal rod cells is described in more detail starting from photon absorption and culminating in ion currents. Dark noise and temperature-dependence of photocurrents in photoreceptor cells are analyzed. Perception of polarized light, its effects and informational importance are discussed based on underlying mechanisms and specialized morphological structures of biological organisms. Role of statistics of photons in photoreception is questioned. The review also pinpoints new and developing directions and raises questions for future research.
Keywords: Photobiology; dark noise; electrophysiology; optogenetics; polarized light; quantum dots; rod cells; statistics of photons.