The word ``radioactive'' appeared for the first time in Pierre and Marie Curie's paper announcing the discovery of Polonium. Starting with the memory of this seminal event and the discovery of Radium, we focus on a few of the tremendous successes achieved in the 30's, namely the successive discoveries of the neutron and the positive electron, followed by the discoveries of artificial radioactivity and later of fission. Experimentalists were confronted with many problems as their interest shifted from radioactivity to ``artificial disintegration'' and cosmic rays experiments. The first discovered \beta ⁺ radioactive isotopes, ³⁰P and ¹³N, and the first fission produced nuclei appear as early steps towards the quest for more and more exotic nuclei.

PACS numbers: 01.65.+g, 25.85.--w, 23.40.--s