Photoreceptors enable most species not only to sense the presence of light, but also information such as irradiance, colour or spectral distribution, direction and polarization of light. They are vital, therefore, in providing organisms with energy and information about their surroundings, such as day and night cycles. Offering comprehensive coverage of the most important areas on photoreceptors and light signalling, this title covers the range of photoreceptors that have been discovered to date and the broad range of methods used when researching how they operate. This includes: action spectroscopy; methods for protein purification; the whole range of molecular biological and genetic methods; and numerous spectroscopic methods, from absorption and fluorescence spectroscopy to X-ray diffraction, used for solving the structure of photoreceptors. Written by experts in the field, the text provides readers with up-to-date results and research and should be of interest to a wide range of readers, including students of photochemistry, photobiology, biology, chemistry and physics and other professionals in academia.