In this paper, we describe the evolution of the eSTEP system. The eSTEP system is an integrated online learning environment for teacher education that provides videocases of classroom practice, an online learning sciences hypertext, and a collaborative problem-based learning environment. The central tool in the problem-based learning environment is the group whiteboard. In face-to-face PBL activities, a whiteboard serves to focus negotiation and represent current understanding. Seeking to offer the same functionality online, we adapted the structure and functionality of a basic whiteboard to easily allow students to exchange and develop ideas online, and effectively represent current understanding. This tool serves as the focus of negotiation in face-to-face PBL but required considerable adaptation to serve this function in an online environment. This paper describes the refinement of the whiteboard and the concomitant refinement of our theory of how students learn through meshing the conceptual ideas of the learning sciences with perceptual information from the problems of practice.