Millions of contemporary young adults use social networking sites. However, little is known about how much, why, and how they use these sites. In this study, 92 undergraduates completed a diary-like measure each day for a week, reporting daily time use and responding to an activities checklist to assess their use of the popular social networking site, Facebook. At the end of the week, they also completed a follow-up survey. Results indicated that students use Facebook approximately 30 min throughout the day as part of their daily routine. Students communicated on Facebook using a one-to-many style, in which they were the creators disseminating content to their friends. Even so, they spent more time observing content on Facebook than actually posting content. Facebook was used most often for social interaction, primarily with friends with whom the students had a pre-established relationship offline. In addition to classic identity markers of emerging adulthood, such as religion, political ideology, and work, young adults also used media preferences to express their identity. Implications of social networking site use for the development of identity and peer relationships are discussed. (Contains 8 tables.)