Hemsworth voices young Optimus Prime, when he was just known as Orion Pax.

Henry is D-16, before he became Optimus’ rival Megatron. The trailer shows the two starting out as simple worker bots, unable to transform into anything. But soon they gain the ability to change into vehicles and gain weapons, as a battle against a mysterious, plant-like villain unfolds on the Transformers’ home planet of Cybertron.

Other cast members include Johansson as Elita, Keegan-Michael Key as Bumblebee, Jon Hamm as Sentinel Prime and Laurence Fishburne as Alpha Trion.

Hemsworth and Henry introduced first look at the prequel film April 11 at CinemaCon.

Bay directed the first five live-action films, with Travis Knight taking over for 2018’s “Bumblebee” and Steven Caple Jr. helming “Transformers: Rise of the Beasts.”

Steven Spielberg is executive producing “Transformers One” with Brian Goldner, Brian Oliver, Bradley J. Fischer and Valerii An. Producers include Lorenzo di Bonaventura, Tom DeSanto, Don Murphy, Michael Bay, Mark Vahradian and Aaron Dem.

“Transformers One” is set to release in theaters Sept. 20.

Watch the trailer below.