What are nuclear isomers? And why are they so awesome?

Nobel laureate Otto Hahn is credited with the discovery of nuclear fission. Fission is one of the most important discoveries of the 20th century, yet Hahn considered something else to be his best scientific work. In 1921, he was studying radioactivity at the Kaiser Wilhelm Institute for Chemistry in Berlin, Germany, when he noticed something he could not explain. One of the elements he was working with wasn’t behaving as it should have. Hahn had unknowingly discovered the first nuclear is