In his famous equation, E=mc2, Albert Einstein established that energy (E) and mass (m) are two forms of the same thing. He showed that tiny particles of matter can be converted into huge amounts of energy.
This discovery helped to unlock the atom and create the field of nuclear energy. It also had a profound impact on our understanding of the universe.
Einstein's work on energy is just one example of his genius. He also made major contributions to the fields of math, physics, and philosophy.