This foundational 2004 study used life history interviews with adult TCKs who were former international school students. Key findings: TCKs struggle with rootlessness and a sense of belonging that spans multiple cultures without fully belonging to any. The study found that ATCKs often felt their rootlessness to be a defining and long-lasting feature of their identity well into adulthood. This is one of the most widely cited studies in the TCK research canon and established the central belonging framework that subsequent research has built upon.