The chapter discusses the second demographic transition, which marks a significant shift in fertility and marriage patterns in Western countries and beyond. This transition, distinct from the first demographic transition, is characterized by sustained sub-replacement fertility, multiple living arrangements, and a disconnection between marriage and procreation. Key features include rising ages at first marriage, increased divorce rates, and a decline in extramarital fertility. The transition is driven by economic development, individual autonomy, and a shift towards higher-order needs, as outlined by Maslow. The theory of the second demographic transition has faced criticism, including claims that it is merely a continuation of the first transition or a secondary feature. However, the author argues that the two transitions are distinct and have different societal implications, such as more pronounced population aging, increased reliance on immigration, and less social cohesion. The diffusion of the second demographic transition is not limited to Northern and Western Europe but has spread to Central and Eastern Europe, Southern Europe, and other regions, with varying degrees of intensity. The chapter also explores the micro-level evidence, showing that value orientations and household choices are influenced by secular and anti-authoritarian sentiments, particularly among younger cohorts.The chapter discusses the second demographic transition, which marks a significant shift in fertility and marriage patterns in Western countries and beyond. This transition, distinct from the first demographic transition, is characterized by sustained sub-replacement fertility, multiple living arrangements, and a disconnection between marriage and procreation. Key features include rising ages at first marriage, increased divorce rates, and a decline in extramarital fertility. The transition is driven by economic development, individual autonomy, and a shift towards higher-order needs, as outlined by Maslow. The theory of the second demographic transition has faced criticism, including claims that it is merely a continuation of the first transition or a secondary feature. However, the author argues that the two transitions are distinct and have different societal implications, such as more pronounced population aging, increased reliance on immigration, and less social cohesion. The diffusion of the second demographic transition is not limited to Northern and Western Europe but has spread to Central and Eastern Europe, Southern Europe, and other regions, with varying degrees of intensity. The chapter also explores the micro-level evidence, showing that value orientations and household choices are influenced by secular and anti-authoritarian sentiments, particularly among younger cohorts.