COMSOL Multiphysics (formerly FEMLAB) is a finite element analysis and solver software package for various physics and engineering applications, especially coupled phenomena, or multiphysics. COMSOL Multiphysics also offers an extensive and well-managed interface to MATLAB and its toolboxes for a large variety of programming, preprocessing and postprocessing possibilities. A similar interface is offered to COMSOL Script. The packages are cross-platform (Windows, Mac, Linux, Unix.) In addition to conventional physics-based user-interfaces, COMSOL Multiphysics also allows for entering coupled systems of partial differential equations (PDEs). The PDEs can be entered directly or using the so called weak form (see finite element method for a description of weak formulation).