MEMENTO (2000): editing

The editing techniques in Christopher Nolan's Memento (2000) seem to serve two core functions: to present multiple versions of reality to the audience, and to arrange the chronology of the movie in a coherent yet ultimately twisted manner. Christopher Nolan uses very short flashbacks to call the true story of Memento into question, "whipping back and forth" through jump cuts "to check for differences in 'repeated' shots". Tiny fragmented shots of Leonard and his wife are replayed near the end of the scene, for instance, with an insulin syringe added into the otherwise completely parallel shot of the memory, questioning the validity of Leonard's pre-accident memories. In one scene in which Sammy is sitting alone in an asylum, "for literally a split second of screen time, we see Leonard himself in Sammy’s chair" as someone walks in front of the camera. This tiny flash of a scene's altered reality, also implemented notably in David Fincher's Fight Club, is what truly convolutes the film's presentation of reality-- in conjunction with Teddy's verbal explanations of Leonard's true story.

Nolan also uses editing techniques to present the film in an interesting chronology. Evoking the themes of memory loss, true knowledge, and confusion; the plot of Memento is shown backwards over a series of short scenes. These scenes move in reverse through time. Spliced between each scene is another timeline, shown in black and white, in which the chronology moves forwards, detailing a conversation that takes place just before any color scenes in the movie. In a masterful scene in which the "beginning" of the color shots meet the "end" of the black and white shots, Leonard takes a polaroid "and the Polaroid’s color image fades in, so does the color of the entire scene", fusing the timelines together. This seamless transition between timelines clarifies the film's confusing relationship with time, leaving the audience with a perception that is still intriguing but ultimately comprehendible.
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Quotations taken from Andy Klein's "Everything You Wanted To Know About Memento": http://www.salon.com/2001/06/28/memento_analysis/