Nikola Tesla was born in Europe in 1856. He emigrated to the U.S. in 1943 to work for Thomas Edison. He died in 1943. He was an electrical engineer, a mechanical engineer and a physicist. He greatest achievement, the way I see it, was the invention of (AC current), that is alternating current, the source of electrical current that powers civilization. Of course (DC) current is important, it is produced by batteries as a source of electrical power, but also it is produced by DC generators.
He achieved other things in his life. I have only mentioned the one thing that impressed me the most, that is, alternating current.