TL;DR:
Nakamura worked for Nichia, stubbornly sought to develop blue LED tech that would be bright enough to be practical and simple/cheap enough to be mass-produced. Against all odds, he built and customized his own oven/tool to revolutionize GaN crystal production that would make the blue LED possible and later, white LEDs. This enabled the world to have home LED lighting and really all modern applications of LED tech in our screens, monitors, TVs, etc.
Side note: He quit Nichia because they allegedly did not pay him for his breakthroughs and he (I think) ended up jumping to CREE. Nichia sued him for leaking company secrets, but he counter-sued for the company not compensating him. The court ruled in Nakamura's favor, but the award only covered his legal fees. So lawyers won, no one else.