What’s an invention that quietly changed the world, but doesn’t get enough credit?

The telegraph. You can Google it, young uns. It first demonstrated how you could communicate rapidly over long distances, shrinking the globe forever after. Led to the telephone, radio, TV, and eventually the Internet and cellphones. Prior to the telegraph it could take days for messages to be conveyed. Battles were fought after wars had ended, just because the word had not gotten to the battlefields. And where would early stock markets have been without the tickertape sharing the latest price fluctuations? News outlets without the "wire services" which earned their nickname because the stories were conveyed by a wire.