This book lays the foundations for you to understand all that you always wanted to know about radioactivity. It begins by setting out essential information about the structure of matter, how radiation occurs and how it can be measured. It goes on to explore the substantial benefits of radioactivity through its many applications, and also the possible risks associated with its use. The field of radioactivity is explained in layman terms, so that everybody who is interested can improve their understanding of issues such as nuclear power, radiation accidents, medical applications of radiation and radioactivity from the environment. Everything is radioactive. There is natural radioactivity in the homes that we live in, the food that we eat and the air that we breath. For over 100 years, people have recognised the potential for radioactivity to help solve problems and improve our standard of living. This has led to the creation of radioactivity levels in some places that are much higher than naturally-occurring background levels. Such high levels of radiation can be harmful to people and the environment, so there is a clear need to manage this potential harm and to make the risk worth the benefits mankind can achieve from radioactive materials.