Albert Einstein publishes on November 21, 1905, as the last of the four papers of his Annus Mirabilis, "Does the Inertia of a Body Depend Upon Its Energy Content?" in Annalen der Physik. The paper, only three pages long, demonstrates that if a body emits energy L in the form of radiation, its mass decreases by L/c². Contrary to popular belief, the equation E=mc² does not appear written in this form in the original paper — Einstein used the notation L for energy — but the result is mathematically equivalent and would become the most famous relation in 20th-century physics. It lays the theoretical framework that makes conceivable, almost three decades later, the release of nuclear energy through transmutation or fission reactions.