This volume contains the lectures given at the NATO Advanced Study Institute on "Biophysics of Photoreceptors and Photomovements in Microorganisms" held in Tir- renia (Pisa), Italy, in September 1990. The Institute was sponsored and mainly funded by the Scientific Affairs Division of NATO; the Physical Science Committee and the Institute of Biophysics of National Research Council of Italy also supported the School and substantially contributed to its success. It is our pleasant duty to thank these institu- tions. Scientists from very different backgrounds contributed to the understanding of...