M. Night Shyamalan's upcoming crossover sequel to "Unbreakable" and "Split," titled "Glass," has started production in Philadelphia.

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The filmmaker announced that filming has commenced on Twitter Tuesday, alongside a photo of a clapperboard featuring a logo for the film.

"Day 1: Seventeen years in the making. #Glass," Shyamalan captioned the image.

Announced in April, "Glass" is scheduled to hit theaters on Jan. 18, 2018 and will work as both a sequel to 2000's "Unbreakable" and 2016's "Split."

The film will revolve around "Unbreakable's" Bruce Willis taking on James McAvoy's villainous character from "Split."

Stars from both films, including Samuel L. Jackson and Anya Taylor-Joy, will also be featured alongside series newcomer Sarah Paulson.