This paper provides an overview of the capabilities of the FreeFem++ software, a powerful tool for solving partial differential equations (PDEs) numerically in two and three dimensions. The author, Frédéric Hecht, highlights the software's adaptability and its ability to handle complex, coupled systems and multiphysics problems. Key features include: 1. **Problem Description**: FreeFem++ allows users to describe problems using variational formulations and access internal vectors and matrices. 2. **Mesh Adaptation**: The software includes tools for mesh adaptation, such as Delaunay-Voronoi algorithms and metric-based methods, to optimize the distribution of errors and improve solution accuracy. 3. **Phase Change with Natural Convection**: An example of solving a phase change problem with natural convection is presented, demonstrating the software's capability to handle nonlinear and complex models. 4. **Schwarz Domain Decomposition**: The paper also showcases a parallel implementation of the Schwarz domain decomposition method, which is efficient for solving large-scale problems. The paper concludes by emphasizing the ongoing development and future enhancements of FreeFem++, including the addition of more tools for anisotropic mesh generation, automatic differentiation, and seamless integration of parallel computing.This paper provides an overview of the capabilities of the FreeFem++ software, a powerful tool for solving partial differential equations (PDEs) numerically in two and three dimensions. The author, Frédéric Hecht, highlights the software's adaptability and its ability to handle complex, coupled systems and multiphysics problems. Key features include: 1. **Problem Description**: FreeFem++ allows users to describe problems using variational formulations and access internal vectors and matrices. 2. **Mesh Adaptation**: The software includes tools for mesh adaptation, such as Delaunay-Voronoi algorithms and metric-based methods, to optimize the distribution of errors and improve solution accuracy. 3. **Phase Change with Natural Convection**: An example of solving a phase change problem with natural convection is presented, demonstrating the software's capability to handle nonlinear and complex models. 4. **Schwarz Domain Decomposition**: The paper also showcases a parallel implementation of the Schwarz domain decomposition method, which is efficient for solving large-scale problems. The paper concludes by emphasizing the ongoing development and future enhancements of FreeFem++, including the addition of more tools for anisotropic mesh generation, automatic differentiation, and seamless integration of parallel computing.