FLUX.3 First Last Frame to Video by Black Forest Labs interpolates between two images you provide, a start frame and an end frame, generating the motion in between plus matching audio. Describe the transition and the sound you want, and the clip resolves precisely on your final frame. Choose a duration from 5 to 20 seconds at 720p or 1080p in aspect ratios from 21:9 to 9:16. Great for controlled reveals, product turns, before-and-after transformations, morphs and match cuts where you need an exact start and end.