This study explores the dynamic, interactive nature of digital drawings and writing in a knowledge building community in which students used a multimedia online environment--Knowledge Forum--to represent and advance ideas in the field of optics. The research employs a mixed-methods case study to collect and analyze multimedia notes created by 22 fourth-grade students. Graphical notes--notes containing drawings--included more idea units and more sophisticated ideas than non-graphical notes. Quality of drawing also correlated with idea improvement in Knowledge Forum notes, with ratings of idea improvement based on conceptual understanding of optics. Overall, findings revealed significant advantages of online drawing for Grade 4 students, with case-study analysis revealing the many ways in which graphics complement writing and contribute to knowledge building.