Multimedia messages should be designed to facilitate multimedia learning processes. This chapter first explores three assumptions underlying a cognitive theory of multimedia learning: dual-channel assumption, limited-capacity assumption and active processing assumption. Three memory stores in the cognitive theory of multimedia learning are: sensory memory, working memory, long-term memory. For meaningful learning to occur in a multimedia environment, the learner must engage in five cognitive processes: selecting relevant words for processing in verbal working memory, selecting relevant images for processing in visual working memory, organizing selected words into a verbal model, organizing selected images into a pictorial model, and integrating the verbal and pictorial representations with each other and with relevant prior knowledge activated from long-term memory. The chapter also explores three demands on cognitive capacity during multimedia learning: extraneous processing, essential processing and generative processing.