This article begins showing that the three distinct, albeit related notions of "ages of life", "family generations", and "social generations" are all integral to the concept of mode of reproduction". Next, it shows that "youth", defined as a sequencewithin biographical trajectories characterized by the double-sided accession to a stable position in the labormarket and matrimonialmarket, can be simultaneously described as a period of "primitive accumulation", "weightlessness" and "status inconsistencies", "social indetermination", "classification" and "the crystallization of habitus".