The heaviest elements in the Universe are unstable: atoms are not immutable as we once thought, they can spontaneously transmute into other elements. Through a process called radioactive decay, heavy nuclei, with many neutrons and protons, transform into lighter ones, releasing highly energetic rays.

Studying radioactive substances, the great Marie Curie discovered two new elements: polonium and radium. She envisioned the medical applications of radioactivity, and created the first mobile X-ray units for diagnosis. In the upcoming decades, as technology progressed, more applications were found based on radioactive decays, from clean nuclear power to tragic nuclear bombs... Fear then started to crawl inside the minds of those who did not dare to understand.