This project uses the German reunification to study how social change impacts two aspects of women's family formation: standardization - the degree to which women's family formation is similar, and pluralization - the development of new family formation patterns. In view of the Second Demographic Transition (SDT), institutional, economic, and ideational explanations for family behavior are discussed. The study proposes a new sequence analytical approach to calculate within and between group differences in family formation trajectories. Findings from the German Life History Study (GLHS) show a rapid de-standardization of family formation among East German women after the reunification. With the breakdown of the communist regime, East German women shifted away from a traditional early marriage pattern to alternative family forms. In contrast, West German women's family formation is more standardized after the reunification than before. They polarize into either a traditional or a delayed family formation pattern. As a result, East and West German women's family formation is just as different in the decades following the reunification as it was in divided Germany. The findings support that de-standardization and pluralization of family formation are transitional features of the SDT with a re-standardization of new family forms, once societies have passed through the SDT.