What is the single most important invention or discovery of all time?

No poll this time — there’s no honest way to narrow “most important, ever” down to a couple of options without cutting someone’s real answer out before the conversation even starts.

It doesn’t have to be the most famous one, or the most recent. It just has to be the one you’d argue actually changed the most, for the most people, for the longest time.

What’s your pick, and what does it beat out?