By progression, I mean furthering the world for its time.
Gutenberg's printing press is usually labeled as the most important overall, but I am sure arguments could be made for tons of stuff.
Automobiles allowed communities to spread out from town centers and job locations to be more than working where you live. The wheel allowed humans to transport everything easier, especially compared to the time period they were in. Heck, even nuclear bombs allowed humanity to truly realize its potential for catastrophic destruction.
Anyway, I would say for modern times, the internet. I think it has honestly helped spread a lot of truth to the world, so people can find out what really happened and get picture information to back it up, instead of being fed whatever the news wants (ignoring countries with heavily censored internet). I also believe it helps people understand other cultures a lot more than a lecture in school does, since you are in contact with people globally (just look at the amount of nations this forum has in it). And essentially if humanity goes under due to nuclear war or something, if the internet could be accessed, it is essentially the bible of all things humans have ever done with wikipedia and how to create things and why things work. A lot more, but there is my two cents.