The document introduces Microsoft Prism, a framework for building modular WPF desktop applications. Prism allows applications to be decomposed into independently-developable modules, provides infrastructure for loading and navigating between modules, and supports practices like MVVM, dependency injection and event aggregation. It facilitates team development by allowing separate teams to work independently on modules while still being able to integrate them into a cohesive application. Prism provides tools that improve reusability, extensibility, flexibility, and quality of modular applications.