This is the ?fth volume in the Reviews in Fluorescence series. To date, four previous volumes have been both published and well received by the scienti?c community. Several book reviews in the last few years have also favorably remarked on the series. In this ?fth volume we continue the tradition of publishing leading edge and timely articles from authors around the world. With the recent Nobel Prize in Chemistry for 2008 being awarded for the discovery and development of the Green Fluorescent Protein (GFP) to Shimomura, Chal?e, and Tsien, we have subsequently included several timely reviews on GFP in this volume. We thank the authors for their timely and exciting contributions. We hope you ?nd this volume as useful as past volumes, which promises to be just as diverse with regard to ?uorescence-based content. Finally, in closing, I would like to thank Caroleann Aitken for helping coordin- ing content with authors and Michael Weston at Springer for help in publishing this current volume. Baltimore, MD, USA Chris D. Geddes v . Contents Fluorescence Anisotropy to Study the Preferential Orientation of Fluorophores in Ordered Bi-Dimensional Systems: Rhodamine 6G/Laponite Layered Films ...1 F. Lopez Arbeloa, V. Martinez, T. Arbeloa, and I. Lopez Arbeloa Room Temperature Tryptophan Phosphorescence of Proteins in the Composition of Biological Membranes and Solutions ...37 Vladimir M. Mazhul', Alexander V. Timoshenko, Ekaterina M.