The Year in Science 2009: What Was Important? What Changed Everything?

It is getting to be that time of year again--that time of year when everybody summarizes the year. So this is an open thread to ask for your picks: What happened in science, technology, and medicine in 2009 that was really important, potentially historic or groundbreaking, or simply worth remarking upon? I certainly have my ideas, but I want to hear what others think as well....