At first a simple employee of the Swiss Patent Office in Bern, the young Einstein published in 1905 a series of scientific articles that questioned everything that was thought to be known in the world of physics. His theory, summed up by the formula E=mc2, opened to humanity the power of the atom. A legendary genius but also a great humanist, he lived through the first half of the 20th century with all its horrors and contradictions, in the service of science but distraught by what man's madness was capable of doing with it.