I Wanna Know What's the Greatest Invention

First would have to be the whole modern electrical distribution system. It allows for so many other useful modern conveniences. I would have to put modern refrigeration at the top of that list. It allows people to store food safely for a much longer period than they ever could without it. It allows people to freeze foods for use long after preparation, or buy them already prepared and frozen. It also allows people the luxury of having a cold, iced drink any time they like. If you have ever sweltered in the heat, unable to drink something cold for a long period of time, you will understand what I mean.