In this session, participants will learn about a National Science Foundation-funded project to develop a smartphone app to visualize magnetic fields with AR. The developers will discuss the opportunities and challenges of working with ARCore and provide visual examples from their recently-developed project, Physics Toolbox AR. They will share their experience of using ARCore in an educational research setting to help learners make sense of fields in 3-D space. Participants will be welcomed to explore the app during an interactive portion of the session. Learn more about this project at https://www.vieyrasoftware.net/physics-toolbox-ar