Problem-based learning demonstrates increased motivation and development of collaboration and problem-solving skills over traditional instruction. Students can master content in an authentic context as they pursue a creative solution to a messy problem. Putting the units in place, though, can be daunting. Come talk with the authors of several PBL units and see some of the Project Parallax curriculum, which won the NAGC Curriculum Studies award in 2010. We will draw on the development and implementation of six elementary PBL STEM units to explore guidelines in unit creation, address the research, and discuss potential pitfalls.