The primary goal of exobiological research is to reach a better understanding of the processes leading to the origin, evolution and distribution of life on Earth or elsewhere in the universe. In this endeavor, scientists from a wide variety of disciplines are involved, such as astronomy, planetary research, organic chemistry, paleontology and the various sub disciplines of biology including microbial ecology and molecular biology. Space technology plays an important part by offering the opportunity for exploring our solar system, for collecting extraterrestrial samples, and for utilizing the peculiar environment of space as a tool. Questions that have been tackled by exobiological experimentation in Earth orbit include the relevance of extraterrestrial organic molecules to the emergence of life on Earth or an any other planet, the role of solar UV radiation in evolutionary processes related to life, and the chances and limits for life to be transported from one body of our solar system to another or beyond. Studies on the responses of microorganisms to the environment of space have been carried out by use of balloons, rockets and spacecrafts. They have demonstrated the enormous lethal potential of extraterrestrial solar UV radiation. However, if shielded against the influx of solar UV, bacterial spores cope with the harsh environment of space for more than 5 years without any loss in viability. Future research e.g. on the International Space Station by use of the SEBA (Space Exposure Biological Assembly) facility will provide further clues to these important exobiological questions.