The story of radium is quite sad. After it was discovered, people were fascinated by this element which glows in the dark. Nobody knew that this was because of its harmful radioactivity. There was a hype around products containing radium, which were sold as cures and cosmetics. Only after workers, who painted glow-in-the-dark paint containing radium onto wrist-watches, began to develop cancer in the mouth, people started to realize that there was something wrong. It turned out that the workers – who were later called "radium girls" – sharpened the brushes with their tongues. Slowly people found out about the danger of the radioactive ray – unfortunately too late for many.