MSTK is a powerful framework for low-level creation and manipulation of unstructured meshes. MSTK is not a mesh generator but it can be used to develop advanced mesh generation software and other mesh-based applications. The salient feature of MSTK is that it is allows multiple mesh representations while presenting a common functional interface to the developer. This allows application developers to use a mesh representation optimized for their particular algorithms. MSTK allows developers to focus on their applications rather than on the details of mesh data structures.