This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The author's main interest is on how thoughts about the future influence present attitudes and behaviors. He was specifically interested in the consequences associated with the knowledge of future mortality. The author assumes that research program on nostalgia would indicate that nostalgia is a very positive emotional experience. More critically, though the work in author's lab was in an early stage, his preliminary results supported the idea that nostalgia has positive psychological effects. The author reviews the many ways that people mitigate the threat of death-awareness. Across the pond at the University of Southampton, UK, social psychologists Constantine Sedikides and Tim Wildschut were also launching a program of research on nostalgia. Social psychology is a small world so pretty soon the authors discovered each other and joined forces. Their goal was to embark on a comprehensive investigation of the psychology of nostalgia.