Marie carried on with her systematic studies on radioactive substances, especially uranium. She realized that pitchblende was four times as active as uranium, and so she concluded that it must contain some other substances. Pierre Curie was so intrigued by her research findings that he decided to join her.
In 1898 they discovered the existence of a new element, which they named "polonium", in honour of Marie's beloved native Poland. A couple of months later they announced the existence of a second element, which they named "radium" for its intense radioactivity.
They had worked with 8 tons of pitchblende with their laboratory equipment until one-tenth of a gram of radium chloride was separated in 1902. In order to conduct their research requiring superhuman efforts, they only managed to set up a laboratory in a shed, where they suffered from every possible kind of inconvenience.