Once married, Pierre and Marie teamed up to conduct research
on radioactive substances.
Marie's attention was drawn to pitchblende or uranium ore whose activity was superior to that of pure uranium. She thought must be due to the presence of small quantities of an unknown substance of very high activity. With the help of Pierre this theory lead to the discovery of
Polonium in the summer of 1898 and Radium a few months later.
Also around this time scientist Antoine Henri Becquerel discovered the phenomenon 'radioactivity'. For his work and for the curies discovery of Radium and Polonium, they received the Nobel prize for Physics in 1903.
Marie then devoted her time to obtaining Radium in its pure metallic state and with the help of A. Debierne, she achieved this in 1911.