Nilsen reconstructs biographical research as an inquiry into the dynamic between individual lives and historical conditions rather than as the recovery of self-contained personal narratives. Her decisive contribution is temporal stratification: biography is intelligible only through the interaction of individual timing, family time, cohort position, institutional change and historical period. The life course is therefore neither a fixed developmental sequence nor a retrospective story of self-realisation. It is a contextual trajectory whose transitions acquire meaning through their relation to changing structures. Methodologically, Nilsen defends biographical interviews, lifelines and mixed forms of evidence while resisting both causal reductionism and an unrestricted constructivism in which factual distinctions dissolve into narrative. The book provides a rigorous bridge between qualitative longitudinal research and historical sociology. Its relevance extends beyond sociology because it offers a precise way to study persistence and change without converting duration into destiny: the same life can be followed through different phases while preserving the asymmetry between event, memory, narration and historical circumstance.