The document summarizes research into how young people between the ages of 18-25 collect, organize, and interact with their personal music collections. It finds that while CD collections were once important, digital music files downloaded online have replaced CDs as the primary format. Participants had large digital music libraries of over 3,000 songs and valued being able to customize playlists and access their entire collections anywhere via portable devices. Music was an important part of both leisure activities and constructing personal space for many participants.