Marvel.com has announced that Iron Man 2 is officially underway, with principle photography beginning today.  Robert Downy, Jr. will return as Tony Stark, Iron Man and Gwyneth Paltrow as his assistant, Pepper Potts, and will feature newcomers, Don Cheadle (replacing Terrance Howard as James Rhodes), Mickey Rourke and Sam Rockwell. The sequel is slated for a May 2010 release.