"Supergirl" and "The Flash" executive producers Greg Berlanti and Andrew Kreisberg previously talked about the possibility of a crossover episode between the two shows. At the Television Critics Association press tour last month, Berlanti said that they have talked internally about a crossover, but while The CW chief Mark Pedowitz is supportive of the idea, they had't had official conversations yet.

Now, CBS and The CW have made it official—Barry Allen aka The Flash (Grant Gustin) will be coming to National City, the home of Kara Danvers (Melissa Benoist).

"We are incredibly excited to announce something that we have dreamed of happening since we started making 'Supergirl'—The Flash and Supergirl are teaming up!" Berlanti and Kreisberg said in a statement (via Entertainment Weekly).

"We want to thank Grant Gustin for making the time to come visit (on top of his already immense workload) and all of the folks at CBS, The CW, Warner Bros., and DC for working this out," they continued. Berlanti and Kreisberg also thanked the fans and journalists who have kept asking for the crossover to happen and that they hope to create an episode "worthy of everyone's enthusiasm and support."

Details about the episode are being kept under wraps, but it was reported that the Flash will be visiting Supergirl's city in the upcoming March 28 episode of the CBS series. There is no word yet on whether Benoist will appear on "The Flash." 

Deadline reports that the one-way crossover is likely in part a matter of budget as filming the CBS show is more expensive than "The Flash." Meanwhile, sources close to the two shows told the website that the in-universe reason for the crossover is that The Flash is able to cross dimensions, while Supergirl cannot. This is said to be in line with the current storyline of The CW show, which features a dimensional rift opened between "Earth One" and "Earth Two" that is connected to Barry's powers.

"The Flash" airs Tuesdays at 8 p.m. on The CW, while "Supergirl" airs Mondays at 8 p.m. on CBS.