In this article, we present our process for developing storylines and we share a planning tool that we have used to connect learning experiences into a coherent storyline that runs throughout a project-based science unit. This process has been used by teachers and researchers to develop project-based science units (Bielik, Damelin, and Krajcik 2018). Throughout this article, we give examples of how storylines helped us design a project-based unit to support the type of three-dimensional learning about energy described in A Framework for K–12 Science Education and the NGSS (NRC 2012; NGSS Lead States 2013).