This chapter discusses important pedagogical and technical aspects for developing a successful online course, and it describes how each of these aspects influenced the development of an online course about nanoscience aimed at teachers. In order to maximize learning in the online setting, the course developer must consider many things including the content, the course layout, avenues for communication, and how to moderate the interactions of all participants. Of significant importance is to ensure a high degree of interactivity in the online environment. Three types of participant interactivity should be considered: interactivity with the content, with the instructor, and with peers. An understanding of the impacts of each of these aspects will help the course developer design a virtual classroom that maximizes the learning of all course participants.