You might ask who is Nikola Tesla.
We have all heard of Thomas Alva Edison - the man behind the first commercially efficient light bulb and the direct current (DC). However, during the same time, Tesla and George Westinghouse - the man who funded Tesla's works - were demonstrating how an alternating current (AC) was more practical to develop since it could transmit electricity to further distances than Edison's direct current and require even thinner wires. This is not unlike other competitions we have seen since then: the VHS/Betamax format war or the Apple vs Microsoft operating system battle or, the more current, Apple and Samsung smartphone war.
The Battle of Currents had begun and in the end the United States electrical grid switched to the AC form of electric power.
Aside from this, Tesla worked on several other things including a tower which