In the early nineteenth century, light, electricity and magnetism were considered as three independent phenomena. While interest in optics was justified by its application to the manufacture of optical instruments, electrical and magnetic phenomena could be interesting for scientists but they had no practical applications. In this work, and after a brief description of the status of electricity, magnetism and optics in the early nineteenth century, the unification of electricity and magnetism is presented with figures like Oersted, Ampère and Faraday, concluding with "Maxwell's synthesis" of electricity, magnetism and light, which was as relevant as "the Newtonian synthesis" of the heaven physics and earth physics. This "Maxwell's synthesis" is one of the greatest achievements in physics, because it did not only unify electrical and magnetic phenomena, but allowed to develop the whole theory of electromagnetic waves, including light. From Maxwell, another hitherto independent field of physics, optics, was to a certain extent included in electromagnetism.
electromagnetism; history of physics; Oersted; Ampère; Faraday; Maxwell