News of Yahoo's acquisition of Tumblr is already official, so today's NYC event will likely shed some light on that $1.1 billion deal. CEO Marissa Mayer will be on hand to address the crowd -- and we'll be there to give you the play-by-play. Will we hear exactly what Yahoo means when it says won't "screw it up?" Will Tumblr CEO be there to contribute his take on the merger? Park your browsers here to find out; the liveblog goes down at 5PM EST.