BundleMaker is a tool to modularize huge existing Java-based applications. While it was originally developed to support the OSGi migration process of the Techniker Krankenkasse's Java application, it is now an open-source tool hosted at http://www.bundlemaker.org. With BundleMaker you can analyze the structure and dependencies of your Java application including its required third party libraries. In addition, you can define various transformations to restructure your system according to your new modularized target architecture. BundleMaker is able to export the whole restructured system into several output formats such as OSGi binary bundles or projects for the Eclipse PDE development tools. Developed as an OSGi/Eclipse-based application itself, BundleMaker is highly customizable to make it a perfect match for a variety of usage scenarios. In this session we will give you an introduction into BundleMaker's ideas and its underlying concepts.