Book excerpt: This is the first volume of new book series on biophysics and biocybernetics, initiated by the Istituto Italiano per gli Studi Filosofici.A main problem in biophysics is the interaction of light information with functional living structures, in order to shape the organism's behaviour. Although the processes of photoreception and phototransduction are articulated in various ways in different living beings — as it is seen in the subdivision of the topics in this volume on microorganisms, invertebrates, and vertebrates — general ways of light signal reception and transduction through light energy, i.e., photosensitive molecule interactions, could be observed. Highly sophisticated advanced techniques are employed in this research field.