"Evolutions" is a title that features stand-alone, out-of-continuity tales from rotating creative teams. Chuck Dixon wrote the first four-part series "Hearts of Steel", revolving around steam-powered Transformers on Earth in the 19th Century, with art by former Dreamwave artist Guido Guidi. It premiered in July 2006. At its conclusion, the publishers warned that they needed to be conservative with alternate-reality stories, because both they and Hasbro did not want to make things too confusing before the 2007 movie was released. For this reason, the series is on hold until after the movie premieres, but a trade paperback has been released.