A trilogy but not in the traditional sequel-like story related sense of the word, more rather a connective work of art based around the same theme. Directed by Alejandro Gonzalez Iñárritu, the "death trilogy" ultimately reveal the prowess of his mastery of intricate and engaging narratives.
Amores Perros (2000)
"Amores Perros," tells three interrelated tales of love-lost, found, and unrequited. Its' timeline is not linear. It curves back on itself, but not in a manner that is intended to confound the audience. The film begins with an pivotal occurrence that happens half-way through the movie, then proceeds to show events that lead up to that moment, and, later, what happens afterwards. - James Berardinelli
21 Grams (2003)
The title of 21 Grams comes from the work of Dr. Duncan MacDougall, who in the early 1900s sought to measure the weight purportedly lost by a human body when the soul departed the body upon death. MacDougall weighed dying patients in an attempt to prove that the soul was material and measurable. Although MacDougall's results varied considerably from 21 grams, for some people this figure has become synonymus with the measure of a soul's weight.
Starring Brad Pitt, Cate Blanchett, Gael García Bernal. In the remote sands of the Moroccan desert, a rifle shot rings out — detonating a chain of events that will link an American tourist couple’s frantic struggle to survive, two Moroccan boys involved in an accidental crime, a nanny illegally crossing into Mexico with two American children and a Japanese teen rebel whose father is sought by the police in Tokyo.