Book excerpt: PROVISIONAL TEXT This open access radiobiology textbook focuses on the various aspects related to Radiobiology. Its aim is to provide the latest and most comprehensive up-to-date resource for students, professors, scientists and medical staff interested in this important discipline. The goal of radiobiological research is to understand better the effects of radiation exposure at the cellular and molecular levels in order to determine the effects on health. Therefore, radiobiology encompasses various disciplines including biology, clinical applications, pharmacy, environmental and space life sciences, which make radiobiology overall a broad and rather complex topic. This textbook aims to provide a solid foundation to those interested in the basics and practice of radiobiology science, and its relevance to clinical applications, environmental radiation research and space research. It is intended to be a learning resource to meet the needs of students, researchers, or any citizen, with an interest in this rapidly evolving discipline and eager to learn more about radiobiology, but it is also a teaching tool with accompanying teaching materials to help educators. This book offers a unique perspective to students and professionals, covering not only radiation biology but also radiation physics, radiation oncology, radiotherapy, radiochemistry, radiopharmacy, nuclear medicine, space radiation biology & physics, environmental radiation protection, nuclear emergency planning, radiation protection, molecular biology, bioinformatics, and DNA repair.