László Jéki, physicist, has drawn our attention to the stunning (and perhaps frightening) fact, that we live in a torrent of radiation. Our knowledge of radiation was gathered in just the last one hundred years, so we tend to think that this is some sort of modern invention - a human creation. On the contrary, radioactivity is part of nature, without it the Earth would not be inhabitable. Human beings, just like all animals, have always lived in radiation. In our thought, the word 'radiation' is right next to the word 'nuclear'. Many people nurture an irrational fear in connection to anything "nuclear", be it a nuclear power plant or a medical test. In the past hundred years, in addition to the well-known weapons created, a large number of useful applications have been developed, many of which have become indispensable.