The purpose of this research was to analyze one 2nd grade teacher's instructional practices as she helped her students co-construct an understanding of nonfiction as a genre. Research was conducted over the course of 14 weeks with 22 students and one teacher. Data were collected from videos of large and small group instruction; videos of the students working together; and pre- and post- interviews of the teacher and students. In addition, field notes and student work were also part of the data corpus. The major findings of the study include: 1) The teacher taught nonfiction in four ways in order to help her students co-construct an understanding of the genre. She taught nonfiction through text features, content, linking fiction and nonfiction, and the process of creating nonfiction books. 2) When selecting nonfiction books for her students, the teacher considered four criteria as important characteristics of the genre to consider. She asked if the book was nonfiction, adhering to the definition we had created, "Nonfiction contains factual information about the world in which nothing is made up." The other three criteria were aesthetics, organization and style, and text consideration. 3) The teacher's close observations of her students' misunderstandings caused her to change her instruction. She changed her instructional practices in response to students not understanding the function of text features and having trouble differentiating between fiction and nonfiction. In addition, she began to study the complexity and, what she referred to as, the consideration of nonfiction books when her students had difficulty reading the complex books in the class. As a result, she changed her instruction by including more considerate nonfiction books and even worked with her students to help them understand what makes a nonfiction book considerate. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]