Donat-P. Hader, Dr. rer. nat., is a Professor of Botany, Department of Botany and Pharmaceutical Biology at the Friedrich-Alexander University at Erlangen, Germany. He received his doctoral degree and his habilitation from the University of Marburg. He had a research associate position at MSU, DOE, East Lansing, U.S.A. and was visiting scientist at the Chemistry Department, Lubbock, TX, U.S.A., CNR Pisa, Italy and the National Research Lab, Okazaki, Japan. Professor Hader has worked on the photomovement of microorganisms, the effect of solar ultraviolet radiation on phytoplankton and is involved in space biology studying the effect of microgravity on motility in flagellates. He is a member of a Committee on Ecology for the German ministry for science and technology, expert for an Enquete commission of the German Parliament and a member of a UNEP commission on the effects of the ozone destruction. One of the tools for his research activities is a real time image analysis system developed over the last fifteen years. He has published over 360 original papers and has been involved in eleven books as author, translator or editor. Michael Lebert, Dr. rer. nat., is a senior scientist at the Department of Botany and Pharmaceutical Biology at the Friedrich-Alexander University at Erlangen, Germany. He received his doctoral degree from the University of Munich. He was a postdoctoral fellow at the WSU, Pullman, U.S.A. Dr. Lebert has worked on environmentally controlled signal transduction chains in microorganisms for 15 years. This includes the relevance of light and gravity on the behavioral reactions of motile protists and bacteria. In addition, he is interested in the effect of ultraviolet radiation on aquatic ecosystems. His special interest is in the interface between biology, electronics and computers.