The European Space Agency made contact with Philae, the first spacecraft ever to land on a comet, for the first time since its November 15 shutdown, their blog post says. The communication lasted 85 seconds. Project manager Stephan Ulamec deemed Philae ready for operations.
Scientists found historical data from Philae that suggests it had been "awake" even earlier, but unable to make contact. Scientists are hopeful that they'll be able to harvest all sorts of comet-related data from Philae now.
For more on how we landed Philae on a comet in the first place — "a little like pushing a college beer fridge out of a slowly orbiting treehouse about six-tenths of a mile above the ground" — read Keith Blanchard's explainer from last year.