Radioactivity and ionising radiation are not specific products of the nuclear industry. Radioactive uranium, which can be found everywhere in the soil and in seawater, and the isotope potassium-40, which emits hundreds of gamma rays per second in our body, are only two echoes of the origin of the universe and the earth, and also testify of the fact that radioactivity was (and is) a crucial phenomenon in the evolution and the development of nature. From the end of the 19th century it became clear that radioactivity could also be used as a scientific application in society and its force when used "improperly" also became apparent. The contributions of Pierre and Marie Curie, Albert Einstein, Heisenberg and many others have made sure that radioactivity is now a manageable and calculable matter. What has been investigated since, and what was -and is- learned from it, will be included in this course.