Radioactivity. It was Marie Curie (1867-1934) who coined the word. She had a right to: she discovered the stuff (along with her husband, Pierre Curie, and Henri Becquerel). She was the first woman to win the Nobel Prize, the first person to win two Nobel Prizes, and is still the only person in history to have won Nobel Prizes in two different scientific fields. First she won it in Physics in 1903 for the discovery of radiation—that was the shared prize with Pierre and Becquerel. Then in 1911 she won the solo prize in Chemistry for her discovery of the elements radium and polonium. Marie freaking Curie, everybody!
The great thing about a Marie Curie costume is that she is so famous, all you really need is a long black dress and a few key props. By which we mean radioactive-looking props, since Madame Curie was soaking in it. It was a long time before people realized that radiation was deadly, so Marie spent years handling radioactive material, carrying it in her pockets, holding it in her hands, looking at it for fun, even keeping a vial of the stuff next to her bed as a nightlight. The items we suggest:
1. Late Victorian/Edwardian dress in black. This simple high-necked dress looks exactly like the kind of thing Marie Curie wore every day in her lab.
2. Victorian/Edwardian button boots in black. Love these boots.
3. Glow Sticks. People think of radiation as glowing green, but actually radium gives off a cool blue light. Whether you choose blue or green, glow sticks are an easy prop for that radioactive look.
4. Volumetric flasks. If you want something that looks more authentically scientific than glow sticks, fix up some flasks with blue liquid inside (next).
4. Blue dish soap. Something like this would look good in your flasks. You can also try bubble solution or Kool-Aid.
6. Optional: Neon blue glitter gel. You could use this in a lot of ways: in your flask, dabbed here and there on your person, that sort of thing. Silly but fun.
