The objective of this course is to provide a comprehensive summary of the biological effects of low and intermediate radiation doses, with particular emphasis on developmental effects caused by an irradiation of either the parental germ cells (hereditary effects) or the embryo at the various developmental stages. Beside hereditary and embryonic effects, a second and important part of the course will consist in an overview of the recent and current research performed at SCK•CEN in the field of oncology, including a large-scale epidemiological study of cancer incidence and mortality among nuclear workers (in collaboration with IARC and WHO) and an introduction to new technologies for cancer treatment such as hadrontherapy or nanobody-based molecular radionuclide therapy. As SCK•CEN is also much involved in space biology programmes, a third part of the course will be devoted to the various aspects covered by this research, from space radiation and dosimetry to space health effects or the control and use of microbes to support human life in space. These three main parts of the course will be completed with an introduction to the international advisory bodies (UNSCEAR and ICRP) as well as with other aspects of the research performed at the SCK•CEN in the field of "non-cancer effects" of ionizing radiation or in radioecology. The lectures will be accompanied by a number of practical lessons in the fields of developmental biology and molecular biology.