It is a surprising and extraordinary fact that Micheal Faraday derived all his insights from creative experiments, precise observations and an understanding of how nature works.
Faraday’s most important invention was and IS the generator. Instead of weak and expensive batteries, the generator opened up the possibility of large scale cheap power. Even today, all electricity produced by generators goes back to the principle of electromagnetic induction discovered by Faraday.
His contribution to humanity is hard to describe with just a few paragraphs. He was also son of a blacksmith, worked at a shop that bound paper into books and was horrible at math.