This chapter introduces a component-oriented approach for developing mixed reality (MR) applications. After a short definition of mixed reality, we present two possible solutions for a component-oriented framework. Both solutions have been implemented in two different MR projects (SAVE and AMIRE). The first project, SAVE, is a safety training system for virtual environments, whereas the goal of the AMIRE project is to develop different authoring tools for mixed reality applications. A component-oriented solution allows developers to implement better designed MR applications, and it fosters the reusability of existing MR software solutions (often called MR gems). Finally, it supports the implementation of adequate visual authoring tools that help end users to develop their own MR applications with no programming skills.