This dissertation presents an empirical study into the figured world of teenage Twitter. Designed as a case study, this study examined the Twitter practices of three teenagers over the course of three years. The larger study contained three distinct investigations. The first study investigated three new literacies practices of multimodal composition in teenage Twitter (i.e., lifeblogging, mirroring, and lifetweeting), finding that these literacies were co-constructed, non-linear, multiple, social, and action-oriented. The second study investigated the relationship between new literacies practices and the identity work that occurs in teenage Twitter, examining how teenagers become feminists through new literacies and their commitments to feminism. This study found that young people's individual experiences and commitments to feminism led to differences in how young people became (or did not) feminist. The third study examined how teaching and learning with Twitter may lead to new relationships between teacher-students, and may even transform traditional power dynamics between teacher and students. It found that the use of teenage Twitter may support engaging, participatory learning that is aligned with humanizing pedagogy. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]