||Life’s strongest storylines are punctuated by and enmeshed with other people. The principle of “linked lives”—that the lives of individuals affect and are affected by the lives of others—is repeated as a mantra in life course literature. And yet this stands in direct contrast to the state of research, which largely treats individuals as if they exist in isolation of others. This author’s wish for the study of human development is to take more seriously the interdependence of lives. To say that lives are “linked” says nothing about their nature, length, purposes, or consequences. The author illustrates the significance of social relationships in time—probing the beginnings, middles, and ends of relationships—and in shaping the life course. It is the author’s hope that developmental science will get better at revealing the intensity and complexity of human life as a social experience.