Life on Earth has evolved and survived for two billion years while constantly exposed to radiation of various kinds. Indeed, light and heat from the sun are natural sources of radiation essential to life and our continued existence.

Different types of radiation can be classified according to the effects they have on matter, including living cells. The two categories of radiation are ionising and non-ionising. lonising radiation includes cosmic rays, X-rays, and the radiation from radioactive materials while non-ionising radiation includes ultraviolet radiation, light, heat, radio waves, and microwaves. Radiations may also be classified in terms of their origin as naturally occurring or artificial (human-made sources of) radiation.

In the modern age, humans have harnessed radiation for use in industry, electricity generation, communications, medicine and even within the home. Without radiation in its various forms, life as we know it would be very different. We use radiowaves for mobile phones, X-rays in medicine and microwaves for cooking, among the very many other uses. These types of radiation are generated by electrical devices and can be controlled or turned off, limiting or stopping the production of radiation.

In contrast, radiation from naturally occurring minerals led to the discovery of radioactivity. Here, unstable atoms spontaneously emit radiation as they seek a more stable state. Unlike artificial sources, this natural radiation cannot be turned off.

The dawn of the nuclear age in the 1940s brought us novel radioactive materials that led to dramatic advances in medical diagnostics and treatment therapies. Such materials are also used in a wide range of processes and procedures, for example, in industry, oil exploration, and life science research.