How can we, as teachers, encourage students to move from drawing geometric objects to constructing them and thereby build their mathematical reasoning skills? One way to encourage students to construct instead of draw shapes and to help students develop more robust understandings of geometric relationships and constructions is to use interactive geometry software, such as The Geometer's Sketchpad (or Sketchpad) or GeoGebra. The activity in this article is an introductory exploration of interactive geometry software (shown here with GeoGebra), an effective probe of students' understanding of basic geometric definitions, and a blueprint for orchestrating a discussion that can help students work on their mathematical reasoning skills. [The activity sheet is online with this article at http://www.nctm.org/mtms. More4u items are available to NCTM members only.]