This chapter reviews the guided discovery principle, according to which guidance should be given to students to ensure effective learning during scientific discovery in multimedia environments. At the heart of these environments often lies a computer simulation that students can use to discover scientific principles through experimentation. The chapter demonstrates the need for and effectiveness of particular types of guidance: process constraints, performance dashboard, prompts, heuristics, scaffolds, and direct presentation of information. Recent research findings that serve to exemplify this typology are discussed. This typology serves as an important first step toward the development of a cognitive theory of adaptive guidance that can determine the appropriate differentiation of instructional support based on the knowledge and skills of individual students. The design of future studies should build on the strengths of current research and avoid some of its weaknesses.