How Radioactivity Was Discovered

In 1895, German physicist Wilhelm Conrad Röntgen discovered a new type of radiation. It was invisible and penetrating to some materials, but not others. He called the radiation "X-rays," and the phenomenon took over the science world. The very next year, a French physicist named Antoine Henri Becquerel, while studying these rays and trying to link them to phosphorescence, accidentally stumbled upon a new phenomenon that would ultimately shape the following century.