The Qatsi trilogy is the informal name given to a series of three films produced by Godfrey Reggio and scored by Philip Glass:

Koyaanisqatsi: Life out of Balance (1982)
Powaqqatsi: Life in Transformation (1988)
Naqoyqatsi: Life as War (2002)

The titles of all three films are words from the Hopi language, in which the word qatsi means "life." More: