Density is a difficult concept for students to understand because it cannot be directly observed. If students are to gain a deeper understanding of the concept of density, they need to learn about density at both the microscopic and macroscopic levels. Virtual reality provides an opportunity for learners to experience phenomena at microscopic scales, so a density exploration simulation was created for use in a Cave Automatic Virtual Environment (CAVE). The research question for this study was: How does the 3D Density CAVE experience impact preservice elementary school teachers' understanding of the density concept at the microscopic level? Three preservice teachers were interviewed before and after their Density CAVE experience. The data collected consisted of participants' recorded audio responses, written texts, and drawings made during the interviews. Thematic analysis was used to explore the raw data. Five major conclusions can be drawn based on the evidence that emerged on participants' conceptualizations of density pre/post the Density CAVE experience: The Density CAVE experience helped participants to (a) visualize water and oil molecules and recognize there are differences in molecular structures, (b) see that molecules of water can have different spacing arrangements, (c) recognize the role of intermolecular forces in the determination of the density of water, (d) recognize that at the microscopic scale, air is not a factor in determining the density of ice. Finally, the Density CAVE experience had no impact on the participants' conceptualization of the role of molecular mass in determining density. Based on this study, students can benefit from having virtual reality experiences such as those in the CAVE to explore density at the microscopic scale. [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.]