Eclipse Sirius is an open source modeling tool that allows users to easily create custom modeling workbenches. It provides a common API that integrates modeling representations and structured data. This allows tool developers to create modeling tools tailored for specific domains and end users' processes using concepts like diagrams, matrices and tables. Sirius also provides features like synchronized editors and validation rules to deal with complex modeling problems. The presentation discusses using Sirius to build the Mindstorms designer tool as a tutorial example and announces upcoming webinars on integrating Xtext editors and visual differencing capabilities into Sirius.