Using iron filings to help visualize a magnetic field seems ordinary now; you may have even done a similar experiment when you were in school. But in the mid-1800s, Michael Faraday's simple drawings helped jump-start a revolution in physicists' understanding of magnetism.

Faraday was no mathematician--it took the British physicist James Clerk Maxwell to outline the working of electricity and magnetism in the abstract. But Faraday's drawings and talks helped laymen achieve a better understanding of these powerful but unseen forces.