Antoine Henri Becquerel, radioactivity, and the foundations of Nuclear Medicine.

Henri Becquerel's discovery of natural radioactivity in 1896 marked a turning point in the history of science and laid the foundation for modern nuclear physics and nuclear medicine. This overview reviews Becquerel's life, his scientific career, and the experiments that led to the identification of spontaneous radiation emitted by uranium compounds. It also highlights the subsequent contributions of Marie and Pierre Curie, who expanded the understanding of radioactivity through the discovery of polonium and radium. Furthermore, the article discusses the early therapeutic applications of radium and the lasting impact of Becquerel's work on diagnostic imaging, radionuclide therapy, and radiation oncology. More than 130 years after his discovery, Becquerel's scientific legacy remains fundamental to contemporary medicine and is commemorated by the SI unit of radioactive activity, the becquerel (Bq).